Rotor-stator structures including boost magnet structures for magnetic regions having angled confronting surfaces in rotor assemblies

ABSTRACT

Various embodiments relate generally to electrodynamic machines and the like, and more particularly, to rotor assemblies and rotor-stator structures for electrodynamic machines, including, but not limited to, outer rotor assemblies and/or inner rotor assemblies with a corresponding stator assembly. In some embodiments a rotor assembly can include magnetically permeable structures having confronting surfaces oriented at an angle to the axis of rotation. A group of magnetic structures can be interleaved with the magnetically permeable structures. The magnetically permeable structures can also include non-confronting surfaces adjacent to which boost magnets are disposed to enhance flux in a flux path passing through magnetic structures that are interleaved with magnetically permeable structures. Further, the rotor assemblies can include a flux conductor shield disposed adjacent to the boost magnets, the flux conductor shield configured to provide return flux paths.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Pat. No. 7,061,152 issued Jun. 13,2006 entitled “Rotor-Stator Structure for Electrodynamic Machines,” U.S.Pat. No. 7,294,948 issued Nov. 13, 2007 entitled “Rotor-Stator Structurefor Electrodynamic Machines,” U.S. Pat. No. 7,982,350 issued Jul. 19,2011, entitled “Conical Magnets and Rotor-Stator Structures forElectrodynamic Machines,” U.S. patent application Ser. No. 13/044,517,filed Mar. 9, 2011 entitled “Rotor-Stator Structures With an Outer Rotorfor Electrodynamic Machines,” U.S. patent application Ser. No.13/044,527, filed Mar. 9, 2011 entitled “Outer Rotor Assemblies forElectrodynamic Machines,” and U.S. patent application Ser. No.13/044,513, filed Mar. 9, 2011 entitled “Rotor-Stator StructuresIncluding Boost Magnet Structures for Magnetic Regions in RotorAssemblies Disposed External to Boundaries of Conically-Shaped Spaces,”all of which are incorporated herein by reference for all purposes.

FIELD

Various embodiments relate generally to electrodynamic machines and thelike, and more particularly, to flux enhancement structures andtechniques in rotor assemblies and rotor-stator structures forelectrodynamic machines, including, but not limited to, outer rotorassemblies.

BACKGROUND

Both motors and generators have been known to use axial-based rotor andstator configurations, which can experience several phenomena duringoperation. For example, conventional axial motor and generatorstructures can experience losses, such as eddy current losses orhysteresis losses. Hysteresis loss is the energy required to magnetizeand demagnetize magnetic material constituting parts of a motor orgenerator, whereby hysteresis losses increase as the amount of materialincreases. An example of a part of a motor that experiences hysteresislosses is “back iron.” In some traditional motor designs, such as insome conventional outer rotor configurations for radial motors, statorsand their windings typically are located within a region having asmaller diameter about the shaft than the rotor. In some instances, astator and the windings are located concentrically within a rotor. Withthe windings located within the interior of at least some conventionalouter rotor configurations, heat transfer is generally hindered when thewindings are energized. Therefore, resources are needed to ensuresufficient heat dissipation from the stators and their windings.

While traditional motor and generator structures are functional, theyhave several drawbacks in their implementation. It is desirable toprovide improved techniques and structures that minimize one or more ofthe drawbacks associated with traditional motors and generators.

BRIEF DESCRIPTION OF THE FIGURES

The various embodiments are more fully appreciated in connection withthe following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is an exploded view of a rotor-stator structure including rotorassemblies in accordance with some embodiments;

FIGS. 2A and 2B depict a pole face and a magnetic region each configuredto form an air gap with the other, according to some embodiments;

FIGS. 3A and 3B depict examples of outer rotor assemblies, according tosome embodiments;

FIGS. 3C to 3D depict an example of a field pole member configured tointeroperate with outer rotor assemblies, according to some embodiments;

FIGS. 3E to 3F depict an example of a field pole member configured tointeroperate with inner rotor assemblies, according to some embodiments;

FIG. 3G depicts field pole members for outer rotor assemblies and innerrotor assemblies, according to some embodiments;

FIG. 3H depicts an example of a rotor structure implementing anarrangement of offset outer rotor assemblies, according to someembodiments;

FIGS. 4A and 4B depict different perspective views of an example of anouter rotor assembly, according to some embodiments;

FIGS. 4C and 4D depict a front view and a rear view of an example of anouter rotor assembly, according to some embodiments;

FIGS. 4E to 4G depict cross-sectional views of an example of an outerrotor assembly, according to some embodiments;

FIGS. 5A and 5B depict different views of an example of a statorassembly, according to some embodiments;

FIG. 6A depicts an outer rotor assembly and a stator assembly configuredto interact with each other, according to some embodiments;

FIGS. 6B to 6C depict cross-sections of field pole members fordetermining a surface area of a pole face, according to someembodiments;

FIG. 6D illustrates a surface area of a pole face determined as afunction of the flux in a coil region and the flux density produced byat least one magnet, the surface area being oriented at angle from areference line, according to some embodiments;

FIG. 7 depicts a cross-section of a rotor-stator structure in whichfield pole members are positioned adjacent to magnetic regions to formair gaps, according to some embodiments;

FIG. 8A depicts cross-sections of rotor-stator structure portionsillustrating one or more flux path examples, according to someembodiments;

FIG. 8B depicts cross-sections of rotor-stator structure portionsillustrating other flux path examples, according to some embodiments;

FIG. 8C is a diagram depicting elements of a structure for a rotorassembly, according to some embodiments;

FIGS. 9A to 9C depict cross-sections of a rotor-stator structure portionillustrating examples of one or more flux path portions, according tosome embodiments;

FIG. 10 depicts a view along an air gap formed between a magnetic regionand a pole face, according to some embodiments;

FIGS. 11A to 11C depict various views of a field pole member, accordingto some embodiments;

FIG. 12 depicts a magnetic region of a rotor assembly as either a northpole or a south pole, according to some embodiments;

FIGS. 13A to 13C depict implementations of a magnet and magneticallypermeable material to form a magnetic region of a rotor assembly,according to some embodiments;

FIGS. 13D to 13E depict examples of various directions of polarizationand orientations of surfaces for magnets and magnetically permeablematerial that form a magnetic region of a rotor assembly, according tosome embodiments;

FIG. 14 is an exploded view of a rotor-stator structure including rotorassemblies in accordance with some embodiments;

FIG. 15 is an exploded view of a rotor-stator structure including rotorassemblies in accordance with some embodiments;

FIG. 16 is an exploded view of a rotor-stator structure including innerrotor assemblies in accordance with some embodiments;

FIG. 17 is a cross-section view of a rotor-stator structure includingboth outer and inner rotor assemblies in accordance with someembodiments;

FIGS. 18A to 18G depict various views of an example of a magneticallypermeable structure (and surfaces thereof) with various structures ofmagnetic material, according to some embodiments;

FIGS. 19A to 19D depict various views of an example of an outer rotorassembly, according to some embodiments;

FIG. 20 depicts an exploded, front perspective view of a portion of anouter rotor assembly, according to some embodiments;

FIG. 21 depicts a portion of an exploded, front perspective view ofanother outer rotor assembly, according to some embodiments;

FIGS. 22A to 22D depict various views of another example of an outerrotor assembly, according to some embodiments;

FIG. 23A is a front view of an outer rotor assembly including examplesof flux conductor shields, according to some embodiments;

FIG. 23B is an exploded, front perspective view of an outer rotorassembly including examples of flux conductor shields, according to someembodiments;

FIG. 23C is an exploded, rear perspective view of an outer rotorassembly including examples of flux conductor shields and return fluxpaths (and portions thereof), according to some embodiments;

FIGS. 24A to 24C depict various views of an example of an inner rotorassembly, according to some embodiments;

FIGS. 25A to 25B depict exploded views of an example of an inner rotorassembly, according to some embodiments; and

FIG. 26 is an exploded view of a rotor-stator structure including innerrotor assemblies in accordance with some embodiments.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings. Note that in the specification most ofthe reference numerals include one or two left-most digits thatgenerally identify the figure that first introduces that referencenumber.

DETAILED DESCRIPTION Definitions

The following definitions apply to some of the elements described withrespect to some embodiments. These definitions may likewise be expandedupon herein.

As used herein, the term “air gap” refers, in at least one embodiment,to a space, or a gap, between a magnet surface and a confronting poleface. Examples of a magnet surface include any surface of magneticmaterial (e.g., a surface of permanent magnet), a surface of an internalpermanent magnet (“IPM”), such as a magnetically permeable materialthrough which flux passes (e.g., the flux being produced by a magneticmaterial), or any surface or surface portion of a “body that produces amagnetic field.” Such a space can be physically described as a volumebounded at least by the areas of the magnet surface and the pole face.An air gap functions to enable relative motion between a rotor and astator, and to define a flux interaction region. Although an air gap istypically filled with air, it need not be so limiting.

As used herein, the term “back-iron” commonly describes a physicalstructure (as well as the materials giving rise to that physicalstructure) that is often used to complete an otherwise open magneticcircuit (e.g., external to a rotor). In particular, back-iron structuresare generally used only to transfer magnetic flux from one magneticcircuit element to another, such as either from one magneticallypermeable field pole member to another, or from a magnet pole of a firstrotor magnet (or first rotor assembly) to a magnet pole of a secondrotor magnet (or second rotor assembly), or both, without an interveningampere-turn generating element, such as coil, between the field polemembers or the magnet poles. Furthermore, back-iron structures are notgenerally formed to accept an associated ampere-turn generating element,such as one or more coils.

As used herein, the term “coil” refers, in at least one embodiment, toan assemblage of successive convolutions of a conductor arranged toinductively couple to a magnetically permeable material to producemagnetic flux. In some embodiments, the term “coil” can be described asa “winding” or a “coil winding.” The term “coil” also includes foilcoils (i.e., planar-shaped conductors that are relatively flat).

As used herein, the term “coil region” refers generally, in at least oneembodiment, to a portion of a field pole member around which a coil iswound.

As used herein, the term “core” refers to, in at least one embodiment, aportion of a field pole member where a coil is normally disposed betweenpole shoes and is generally composed of a magnetically permeablematerial for providing a part of a magnetic flux path. The term “core,”in at least one embodiment, can refer, in the context of a rotor magnet,including conical magnets, to a structure configured to support magneticregions. As such, the term core can be interchangeable with the term“hub” in the context of a rotor magnet, such as a conical magnet.

As used herein, the term “field pole member” refers generally, in atleast one embodiment, to an element composed of a magnetically permeablematerial and being configured to provide a structure around which a coilcan be wound (i.e., the element is configured to receive a coil forpurposes of generating magnetic flux). In particular, a field polemember includes a core (i.e., core region) and at least one pole shoe,each of which is generally located near a respective end of the core.Without more (e.g., without a coil formed on thereon), a field polemember is not configured to generate ampere-turn flux. In someembodiments, the term “field pole member” can be described generally asa “stator-core.”

As used herein, the term “active field pole member” refers, in at leastone embodiment, to an assemblage of a core, one or more coils, and atleast two pole shoes. In particular, an active field pole member can bedescribed as a field pole member assembled with one or more coils forselectably generating ampere-turn flux. In some embodiments, the term“active field pole member” can be described generally as a “stator-coremember.”

As used herein, the term “ferromagnetic material” refers, in at leastone embodiment, to a material that generally exhibits hysteresisphenomena and whose permeability is dependent on the magnetizing force.Also, the term “ferromagnetic material” can also refer to a magneticallypermeable material whose relative permeability is greater than unity anddepends upon the magnetizing force.

As used herein, the term “field interaction region” refers, in at leastone embodiment, to a region where the magnetic flux developed from twoor more sources interact vectorially in a manner that can producemechanical force and/or torque relative to those sources. Generally, theterm “flux interaction region” can be used interchangeably with the term“field interaction region.” Examples of such sources include field polemembers, active field pole members, and/or magnets, or portions thereof.Although a field interaction region is often referred to in rotatingmachinery parlance as an “air gap,” a field interaction region is abroader term that describes a region in which magnetic flux from two ormore sources interact vectorially to produce mechanical force and/ortorque relative to those sources, and therefore is not limited to thedefinition of an air gap (i.e., not confined to a volume defined by theareas of the magnet surface and the pole face and planes extending fromthe peripheries between the two areas). For example, a field interactionregion (or at least a portion thereof) can be located internal to amagnet.

As used herein, the term “generator” generally refers, in at least oneembodiment, to an electrodynamic machine that is configured to convertmechanical energy into electrical energy regardless of, for example, itsoutput voltage waveform. As an “alternator” can be defined similarly,the term generator includes alternators in its definition.

As used herein, the term “magnet” refers, in at least one embodiment, toa body that produces a magnetic field externally unto itself. As such,the term magnet includes permanent magnets, electromagnets, and thelike. The term magnet can also refer to internal permanent magnets(“IPMs”), surface mounted permanent magnets (“SPMs”), and the like.

As used herein, the term “motor” generally refers, in at least oneembodiment, to an electrodynamic machine that is configured to convertelectrical energy into mechanical energy.

As used herein, the term “magnetically permeable” is a descriptive termthat generally refers, in at least one embodiment, to those materialshaving a magnetically definable relationship between flux density (“B”)and applied magnetic field (“H”). Further, the term “magneticallypermeable” is intended to be a broad term that includes, withoutlimitation, ferromagnetic materials such as common lamination steels,cold-rolled-grain-oriented (CRGO) steels, powder metals, soft magneticcomposites (“SMCs”), and the like.

As used herein, the term “pole face” refers, in at least one embodiment,to a surface of a pole shoe that faces at least a portion of the fluxinteraction region (as well as the air gap), thereby forming oneboundary of the flux interaction region (as well as the air gap). Insome embodiments, the term “pole face” can be described generally asincluding a “flux interaction surface.” In one embodiment, the term“pole face” can refer to a “stator surface.”

As used herein, the term “pole shoe” refers, in at least one embodiment,to that portion of a field pole member that facilitates positioning apole face so that it confronts a rotor (or a portion thereof), therebyserving to shape the air gap and control its reluctance. The pole shoesof a field pole member are generally located near one or more ends ofthe core starting at or near a coil region and terminating at the poleface. In some embodiments, the term “pole shoe” can be describedgenerally as a “stator region.”

As used herein, the term “soft magnetic composites” (“SMCs”) refers, inat least one embodiment, to those materials that are comprised, in part,of insulated magnetic particles, such as insulation-coated ferrouspowder metal materials that can be molded to form an element of thestator structure.

Discussion

FIG. 1 is an exploded view of a rotor-stator structure including rotorassemblies in accordance with some embodiments. Various embodimentsrelate generally to electrodynamic machines and the like, and moreparticularly, to rotor assemblies and rotor-stator structures forelectrodynamic machines, including, but not limited to, outer rotorassemblies and/or inner rotor assemblies. In some embodiments, a rotorfor an electrodynamic machine includes a rotor assembly. FIG. 1 depictsa rotor structure including at least two rotor assemblies 130 a and 130b mounted on or affixed to a shaft 102 such that each of rotorassemblies 130 a and 130 b are disposed on an axis of rotation that canbe defined by, for example, shaft 102. A stator assembly 140 can includeactive field pole members arranged about the axis, such as active fieldpole members 110 a, 110 b, and 110 c, and can have pole faces, such aspole face 114, formed at the ends of respective field pole members 111a, 111 b, 111 c. Active field pole members include a coil 112. A subsetof pole faces 114 of active field pole members 110 a, 110 b, and 110 ccan be positioned to confront the arrangement of magnetic regions 190 inrotor assembly 130 a to establish air gaps. Note that a subset of polefaces 114 can be disposed internally to a conically-shaped boundary 103,such as either conically-shaped boundary 103 a or conically-shapedboundary 103 b. For example, the subset of pole faces 114 can bedisposed at, within, or adjacent to at least one of boundaries 103 a or103 b to form conically-shaped spaces. Either of boundaries 103 a or 103b can circumscribe or substantially circumscribe a subset of pole faces114 and can be substantially coextensive with one or more air gaps. Forexample, the term “substantially circumscribe” can refer to a boundaryportion of conically-shaped space that encloses surface portions of thesubset of pole faces 114. As shown, at least one of boundaries 103 a and103 b form a conically-shaped space and can be oriented at an angle Afrom the axis of rotation 173, which can be coextensive with shaft 102.As shown, boundary 103 a is at an angle A and extends from an apex 171 aon axis of rotation 173 in a direction toward apex 171 b, which is theapex of a conically-shaped boundary 103 b. As shown, conically-shapedboundaries 103 a and 103 b each include a base 175 (e.g., perpendicularto shaft 102) and a lateral surface 177. Lateral surfaces 177 can becoextensive with conically-shaped boundary 103 a and 103 b to formconically-shaped spaces. Note that while conically-shaped boundary 103 aand conically-shaped boundary 103 b each is depicted as including base175, conically-shaped boundary 103 a and conically-shaped boundary 103 bcan extend (e.g., conceptually) to relatively larger distances such thatbases 175 need not be present. Thus, conically-shaped boundary 103 a canextend to encapsulate apex 171 b and conically-shaped boundary 103 b canextend to encapsulate apex 171 a. Note, too, that in some embodiments,at least a portion of pole face 114 can include a surface (e.g., acurved surface) oriented in a direction away from an axis of rotation.The direction can be represented by a ray 115 a as a normal vectorextending from a point on a plane that is, for example, tangent to theportion of pole face 114. Ray 115 a extends from the portion of poleface 114 in a direction away from the axis of rotation and shaft 102.Note that ray 115 a can lie in a plane that includes the axis ofrotation. Similarly, ray 115 b can extend from the other pole faceoutwardly, whereby ray 115 b can represent a normal vector oriented withrespect to a tangent plane 192.

Each rotor assembly can include an arrangement of magnetic regions 190.Magnetic region 190 (or a portion thereof) can constitute a magnet polefor rotor assembly 130 a or rotor assembly 130 b, according to someembodiments. In one or more embodiments, at least one magnetic region190 has a surface (or a portion thereof) that is coextensive (or issubstantially coextensive) to one or more angles with respect to theaxis of rotation or shaft 102. In the example shown, one or moremagnetic regions 190 of rotor assembly 130 a can be disposed externallyto a portion of a conically-shaped space (e.g., a conically-shaped spaceassociated with either conically-shaped boundary 103 a orconically-shaped boundary 103 b) that is centered on the axis ofrotation. In some embodiments, the arrangement of magnetic regions 190can be mounted on, affixed to, or otherwise constrained by a supportstructure, such as either support structure 138 a or support structure138 b. Support structures 138 a and 138 b are configured to supportmagnetic regions 190 in compression against a radial force generated bythe rotation of rotor assemblies 130 a and 130 b around the axis ofrotation. In at least some cases, support structures 138 a and 138 balso can provide paths for flux. For example, support structures 138 aand 138 b can include magnetically permeable material to complete fluxpaths between poles (e.g., magnetic regions and/or magnets) of rotorassemblies 130 a and 130 b. Note that support structures 138 a or 138 bneed not be limited to the example shown and can be of any variedstructure having any varied shapes and/or varied functionality that canfunction to at least support magnetic regions 190 in compression duringrotation. Magnetic regions 190 can be formed from magnetic material(e.g., permanent magnets) or magnetically permeable material, or acombination thereof, but is not limited those structures. In someembodiments, magnetic regions 190 of FIG. 1 can be representative ofsurface magnets used to form the poles (e.g., the magnet poles) of rotorassemblies 130 a and 130 b, whereby one or more surface magnets can beformed, for example, using magnetic material and/or one or more magnets(e.g., permanent magnets), or other equivalent materials. In someembodiments, the term “magnetic material” can be used to refer to astructure and/or a composition that produces a magnetic field (e.g., amagnet, such as a permanent magnet). In various embodiments, magneticregions 190 of FIG. 1 can be representative of one or more internalpermanent magnets (“IPMs”) (or portions thereof) that are used to formthe poles of rotor assemblies 130 a and 130 b, whereby one or moreinternal permanent magnets can be formed, for example, using magneticmaterial (e.g., using one or more magnets, such as permanent magnets)and magnetically permeable material, or other equivalent materials.According to at least some embodiments, the term “internal permanentmagnet” (“IPM”) can refer to a structure (or any surface or surfaceportion thereof) that produces a magnetic field, an IPM (or portionthereof) including a magnetic material and a magnetically permeablematerial through which flux passes (e.g., at least a portion of the fluxbeing produced by the magnetic material). In various embodiments,magnetic material of a magnetic region 190 can be covered bymagnetically permeable material, such that the magnetically permeablematerial is disposed between the surfaces (or portions thereof) ofmagnetic region 190 and respective air gaps and/or pole faces. In atleast some cases, the term “internal permanent magnet” (“IPM”) can beused interchangeably with the term “interior permanent magnet.” Whilethe rotor-stator structure of FIG. 1 is shown to include three fieldpole members and four magnetic regions, a rotor-stator structureaccording to various embodiments need not be so limited and can includeany number of field pole members and any number of magnetic regions. Forexample, a rotor-stator structure can include six field pole members andeight magnetic regions.

As used herein, the term “rotor assembly” can refer to, at least in someembodiments, to either an outer rotor assembly or an inner rotorassembly, or a combination thereof. A rotor assembly can include asurface portion that is coextensive with a cone or a boundary of aconically-shaped space, and can include magnetic material and,optionally, magnetically permeable material as well as other materials,which can also be optional. Therefore, a surface portion of a rotorassembly can be either coextensive with an interior surface or anexterior surface of a cone. An outer rotor assembly includes magneticregions 190 disposed “outside” the boundaries of the pole faces relativeto the axis of rotation. Rotor assemblies 130 a and 130 b are “outerrotor assemblies” as magnetic regions 190 are disposed or arrangedexternally to or outside a boundary 103 of a conically-shaped space,whereas pole faces 114 are located within boundary 103 of theconically-shaped space (i.e., portions of magnetic regions 190 arecoextensive with an exterior surface of a cone, whereas portions of polefaces 114 are coextensive with an interior surface of a cone). As such,a point on the surface of magnetic region 190 is at a greater radialdistance from the axis of rotation than a point on pole face 114, whereboth points lie in a plane perpendicular to the axis of rotation. Anouter rotor assembly can refer to and/or include an outer rotor magnet,according to at least some embodiments. Further, note that the term“rotor assembly” can be used interchangeably with the term “rotormagnet,” according to some embodiments.

The term “inner rotor assembly” can refer to, at least in someembodiments, portions of rotor structures in which magnetic regions aredisposed internally to or “inside” a boundary of a conically-shapedspace, whereas the pole faces are located externally to or outside theboundary of conically-shaped space. As such, a point on the surface ofthe magnetic region is at a smaller radial distance from the axis ofrotation than a point on a pole face, where both points lie in a planeperpendicular to the axis of rotation. An inner rotor assembly can referto and/or include an inner rotor magnet, according to at least someembodiments. To illustrate, FIG. 16 depicts boundaries 1603 ofconically-shaped spaces in which magnetic regions 1690 are disposed.Pole faces 1614 are disposed or arranged outside boundaries 1603 ofconically-shaped spaces. Thus, magnetic regions 1690 are coextensivewith an interior surface of a cone, whereas pole faces 1614 arecoextensive with an exterior surface of a cone). In some embodiments,the term “inner rotor assembly” can refer to either an “inner rotormagnet” or a “conical magnet” or a “conical magnet structure.” Anexample of the structure of a conical magnet can include an assembly ofmagnet components including, but not limited to, magnetic regions and/ormagnetic material and a support structure. In some instances, thesupport structure for an inner rotor assembly or conical magnet can bereferred to as a “hub,” or, in some cases, a “core.” In at least someembodiments, the term “inner rotor assembly” can be used interchangeablywith the terms “conical magnet” and “conical magnet structure.” In atleast one embodiment, the term “inner rotor assembly” can refer, but arenot limited to, at least some of the magnets described in U.S. Pat. No.7,061,152 and/or U.S. Pat. No. 7,294,948 B2. According to a specificembodiment, a rotor assembly can also refer to an outer rotor assemblycombined with an inner rotor assembly.

In view of the foregoing, the structures and/or functionalities of anouter rotor assembly-based motor can, among other things, enhance torquegeneration and reduce the consumption of manufacturing resources. Massin an outer rotor assembly is at a greater radial distance than an innerrotor assembly, thereby providing increased inertia and torque forcertain applications. Again, support structures 138 can be alsoconfigured to support magnetic region and associated structures incompression against radial forces during rotation, thereby enablingoptimal tolerances for the dimensions of the air gap formed between polefaces and magnetic regions. In particular, rotational forces tend tourge the surfaces of magnetic regions 190 away from the surfaces of thepole face surfaces, thereby facilitating air gap thicknesses thatotherwise may not be available. As such, outer rotor assemblies can beused in relatively high speed applications (i.e., applications in whichhigh rotational rates are used), such as in electric vehicles. In someembodiments, a rotor assembly, as described herein, has magneticmaterial (e.g., magnets, such as permanent magnet structures) havingsurfaces that are polarized in a direction such that flux interacts viaat least one side of a magnetically permeable material. For example thedirection of polarization of the magnetic material can be orthogonal orsubstantially orthogonal to a line or a line portion extending axiallybetween two pole faces of a field pole member. The line or the lineportion extending axially between the two pole faces of the field polemember can be oriented parallel to an axis of rotation. As such, thesurface area of the magnetic region can be configured to be less thanthe combined surfaces areas of the magnetic material. For example, thecombined surface areas of the magnetic material surfaces adjacent to themagnetically permeable material can be greater than the surface area ofthe magnetically permeable material that confronts the pole faces.Therefore, the amount of flux passing between the surface of themagnetically permeable material and a pole face can be modified (e.g.,enhanced) as a function, for example, of the size of the surfacesarea(s) of the magnetic material and/or the surface area(s) of the sidesof magnetically permeable material. Also, the type of magnetic material(e.g., ceramic, rare earth, such as neodymium and samarium cobalt, etc.)can be selected to modify the amount of flux passing through a magneticregion. Accordingly, the angle of the conically-shaped space can bemodified (e.g., to a steeper angle, from 45 degrees to 60 degreesrelative to the axis of rotation) to form a modified angle. The modifiedangle relative to an axis of rotation can serve to define theorientation of either an angled surface (e.g., a conical surface) ofmagnetic region or a pole face, or both. With the modified angle, therotor-stator structure can be shortened, which, in turn, conservesmanufacturing materials (i.e., increasing the angle to a steeper angle,the field pole members of a stator assembly can be shortened). The angleof the conically-shaped space can be modified also to enable the use ofless powerful magnets (e.g., ceramic-based magnets, such as ceramicferrite magnets). For example, decreasing the angle from a relativelysteep angle (e.g., 65 degrees) to a more shallow angle (e.g., 40degrees), less powerful magnets can be used as the surface area of themagnets or magnetic regions can be increased to provide a desired fluxconcentration. Therefore, neodymium-based magnets can be replaced withceramic-based magnets. In sum, the modified angle can be a function ofone or more of the following: (i.) the type of magnet material, (ii.)the surface area of the magnet material, (iii.) the surface area ofmagnetically permeable material, (iv.) the surface area of the magneticregion, and (v.) the surface area of a pole face. In some embodiments,the modified angle can be a non-orthogonal angle. Examples ofnon-orthogonal angles include those between 0 degrees and 90 degrees(e.g., excluding both 0 degrees and 90 degrees), as well asnon-orthogonal angles between 90 degrees and 180 degrees (e.g.,excluding both 90 degrees and 180 degrees). Any of these aforementionednon-orthogonal angles can describe the orientation of pole face andmagnetic regions for either outer rotor assemblies or inner rotorassemblies, or both.

Note that in some embodiments, boost magnets can be implemented toenhance the amount of flux passing between a magnetic region and a poleface, whereby the enhancement to the amount of flux by one or more boostmagnets can influence the angle and/or surface areas of the magneticregion or the pole face. Boost magnets can include magnetic materialdisposed on non-confronting surfaces of magnetic permeable material thatare oriented off of a principal flux path. Boost magnets can includeaxial and radial boost magnets, examples of which are shown in FIG. 18Cand subsequent figures. Therefore, the modified angle can also be afunction of the characteristics of boost magnets. For example, the typeof magnet material constituting the boost magnets, the surface area ofthe boost magnets, and the surface area of magnetically permeablematerial adjacent to the boost magnets can influence or modify theamount of flux passing through a magnetic region.

In various embodiments, the angle of the conically-shaped space can bemodified to determine an angle that provides for an optimal surface areaof a pole face through which flux passes, the flux being at least afunction of the magnetic material (e.g., ceramic versus neodymium). Inone approach, the modified angle can be determined by the following.First, an amount of flux in a coil region of an active field pole membercan be determined, the amount of flux producing a desired value oftorque. A magnet material to produce a flux density at an air gap formedbetween a surface of the magnet material and a pole face of the activefield pole member can be selected. Then, the surface area of the poleface can be calculated based on the flux in the coil region and the fluxdensity of the magnet material, the surface area providing for the fluxdensity. Then, the pole face (and the angle of the conically-shapedspace) can be oriented at a non-orthogonal angle to the axis of rotationto establish the surface area for the pole face. In some embodiments,the magnets of a rotor assembly can include an axial extension area thatcan be configured to increase an amount of flux passing through thesurface of the magnetically permeable structure by, for example,modifying the area dimension laying in planes common to the axis ofrotation.

A stator assembly, according to some embodiments, can use field polemembers that can use less material to manufacture than field polemembers configured for other motors. Further, a field pole member for anouter rotor assembly-based rotor-stator structure can have wider andshorter laminations at distances farther from the axis of rotation thanother laminations located at distances closer to the axis of rotation.In turn, flux passing through the field pole member is more uniformlydistributed and is less likely to have high flux densities at certainportions of the field pole member. In some embodiments, the structure offield pole member can be shorter than in other motors, as there can begreater amounts of available surface area of magnetically permeablematerial in the rotor of the rotor-stator structure. The availablesurface area of magnetically permeable material presents opportunitiesto enhance the flux concentration by way of the use of magnetic materiallocated adjacent to the available surface area. In turn, the enhancedflux concentration facilitates the use of pole faces that are coincidentwith a steeper angle relative to an axis of rotation. Steeper-angledpole faces can provide for shorter field pole member lengths and, thus,shorter motor lengths relative to pole faces coincident with less steepangles. According to some embodiments, a field pole member can beconfigured as an outwardly-facing field pole member having a pole faceoriented in a direction away from an axis of rotation. Such a pole facecan have a convex-like surface, but need not be so limited (e.g., a poleface can be relatively flat in rotor-stator structures implementing oneor more outer rotors). This structure provides for flux paths throughthe field pole member that, on average, are shorter than found in otherstator assemblies of comparable length along an axis of rotation.Consider that the surface area of an outwardly-facing pole face can becomposed (conceptually) of a number of unit areas of comparable size,whereby a total flux passing through a pole face passes into a greaterquantity of unit areas associated with relatively shorter flux pathlengths than in other stator assemblies. With flux passing overrelatively shorter flux paths, the flux passes through less materialthan otherwise might be the case. Therefore, losses, such as eddycurrent losses, are less than other stator assemblies that might haveflux paths that, on average, are longer than those associated with theoutwardly-facing field pole member (having a similar axial length).Further, an outwardly-facing field pole member can have less surfacearea (e.g., between the coils and pole faces) adjacent a perimeter of astator assembly than other stator assemblies. Therefore, anoutwardly-facing field pole member can have fewer magnetic linkage pathsthat extend through a motor case, thereby reducing losses and eddycurrents that otherwise might be generated in the motor case.

FIGS. 2A and 2B depict a pole face and a magnetic region, respectively,each being configured to form an air gap with the other, according tosome embodiments. FIG. 2A depicts a pole face 214 being formed as one oftwo pole faces for an active field pole member 210, which also includesa coil 212. Pole face 214 can have a surface (or a portion thereof) thatis curved or rounded outward from the interior of active field polemember 210. In some examples, at least a portion of pole face 214 has acurved surface that is coextensive with one or more arcs 215 radiallydisposed (e.g., at one or more radial distances) from the axis ofrotation, and/or is coextensive with either an interior surface (or anexterior surface) of a cone. Although the field pole member of activefield pole member 210 can be composed of a contiguous piece ofmagnetically permeable material (e.g., a piece formed by a metalinjection molding process, forging, casting or any other method ofmanufacture), the field pole members described herein can also becomposed of multiple pieces, such as laminations, wires, or any otherflux conductors. Therefore, active field pole member 210 can be formedas a stacked field pole member composed of a number of laminationsintegrated together.

FIG. 2B depicts a magnetic region 232 including a magnet surface 233being formed as one of a number of magnetic regions (not shown) thatconstitute a rotor assembly 230. As shown, rotor assembly 230 includes asupport structure 238 for supporting magnetic region 232, among otherthings, to position magnetic region 232 at a distance from pole face 214of FIG. 2A to establish an air gap. Support structure 238 can be alsoconfigured to support magnetic region 232 in compression against radialforces during rotation, thereby enabling optimal tolerances for thedimensions of the air gap formed between pole face 214 and magneticregion 232. Support structure 238 includes an opening 239 at which rotorassembly 230 can be mounted to a shaft. In some embodiments, supportstructure 238 can provide a flux path (e.g., a return path) tomagnetically couple magnetic region 232 to another magnetic region notshown. At least a portion of surface 233 can be coextensive (orsubstantially coextensive) to an angle with respect to the axis ofrotation (or shaft 102 of FIG. 1) passing through opening 239. Whilesurface 233 of magnetic region 232 is depicted as a single, curvedsurface, this depiction is not intended to be limiting. In someembodiments, surface 233 of magnetic region 232 can include surfaces ofmultiple magnets (not shown) that are configured to approximate a curvedsurface that is substantially coextensive with one or more angles withthe axis of rotation, the curved surface being configured to confront apole face. The multiple magnets can include relatively flat surfacemagnets, or can include magnets having any type of surface shape.

FIGS. 3A and 3B depict examples of outer rotor assemblies, according tosome embodiments. FIG. 3A is a diagram 300 depicting a stator assembly340 that includes a number of field pole members, such as field polemembers 310 a and 310 b, and outer rotor assembly 330. In the exampleshown, outer rotor assembly 330 includes an arrangement of internalpermanent magnet (“IPM”) structures. In this example, the radial edgesof magnetic region 390 are shown to be approximately half (i.e., ½) thewidth (e.g., peripheral width) of surfaces 393 a and 393 b of respectivestructures of magnetic material 332 a and 332 b that confront the statorassembly. Thus, the surface of magnetic region 390 can include a surfaceof a magnetically permeable structure and surface portions of magneticmaterial 332 a and 332 b. For example, outer rotor assembly 330 caninclude structures (e.g., magnets) including magnetic material 332, andmagnetically permeable structures 334. Thus, outer rotor assembly 330includes an arrangement of magnetic regions 390 configured to confront asubset of pole faces of stator assembly 340, whereby at least onemagnetic region 390 includes a magnet 332 a (or a portion thereof), amagnetically permeable structure 334 a, and a magnet 332 b (or a portionthereof). Note that a magnetic region is not limited to the exampleshown nor is limited to structures herein. For example, a magneticregion can include one magnet and one magnetically permeable structure.In other embodiments, a magnetic region can include any number ofmagnets and any number of magnetically permeable structures. Further,the term “magnetic region” can refer to the combination of magnets andmagnetically permeable structures (e.g., used to form a magnet pole), orthe combination of structures including magnetic material andmagnetically permeable material. In some cases, a magnetic region canrefer to those surfaces constituting a pole, or can refer to thosesurfaces or structures used to generate a pole, or both. A magneticregion can also be referred to as the surface of a magneticallypermeable structure, and may or may not include surfaces 393 a and 393 bof magnetic material 332 a and 332 b or respective magnets. Thus, thesurface of a magnetic region can be coextensive with the surface of 334a confronting stator assembly 340. In at least one embodiment, magneticmaterial 332 has an axial length dimension 303 that is configurable tomodify an amount of flux density passing through a surface of amagnetically permeable structure, such as through surface 391 ofmagnetically permeable structure 334 a. In some embodiments, structuresof magnetic material 332 a and 332 b are polarized to produce magnetflux circumferentially within outer rotor assembly 330 about an axis ofrotation (not shown).

FIG. 3B is a diagram 330 depicting a rotor-stator structure including anouter rotor assembly 380 a, a group 342 of field pole members, and anouter rotor assembly 380 b. Outer rotor assembly 380 a includes magneticmaterial 382 a and magnetically permeable structures 384 a, whereasouter rotor assembly 380 b includes magnetic material 382 b andmagnetically permeable structures 384 b. A first subset of pole faces364 a are configured to confront surfaces of magnetic material 382 a andmagnetic permeable structures 384 a, and a second subset of pole faces364 b are configured to confront surfaces of magnetic material 382 b andmagnetic permeable structures 384 b.

FIGS. 3C to 3D depict an example of a field pole member configured tointeroperate with outer rotor assemblies, according to some embodiments.As shown, FIGS. 3C and 3D depict field pole member 352 being anoutwardly-facing field pole member with a pole face being oriented in adirection away from an axis of rotation 345. A pole face 350 a is shownto include—at least conceptually—a number of unit areas each associatedwith a length (e.g., a length of a flux path or portion thereof) betweenpole faces 350 a and 350 b of FIG. 3D. Note that the units of area inFIG. 3C are not drawn to scale and each is equivalent to the other unitareas. Pole face 350 a includes a unit area 302 and a unit area 304. InFIG. 3D, unit area 302 is associated with a length 309 between unit area302 of pole face 350 a and unit area 305 of pole face 350 b. Similarly,unit area 304 is associated with a length 308 between unit area 304 ofpole face 350 a and unit area 307 of pole face 350 b. Length 308 isrelatively shorter than length 309. As such, flux passing over length308 has a relatively shorter flux path than if the flux passed overlength 309. Each unit area of pole face 350 a is associated with alength extending to another unit area of pole face 350 b.

Field pole member 352 can be characterized by a mean or average lengthper unit area, which can be determined by adding the lengths associatedwith each of the unit areas and dividing the sum by the number of unitareas in pole face 350 a. The average length per unit area is indicativeof the amount of material, such as magnetically permeable material,contained within field pole member 352. Flux, such as a unit of flux(e.g., unit of total flux), extending along a certain average length perunit experiences less losses, such as eddy current or hysteresis losses,than a longer average length per unit area. When pole face 350 aconfronts a magnetic region that produces a flux density over thesurface area of pole face 350 a, a total flux passes via an air gap (notshown) through field pole member 352. Another characteristic of fieldpole member 352 is that if pole face 350 a is divided axially into twoequal halves (i.e., an upper half 312 and a lower half 311) along theaxis, then upper half 312 is associated with more units of areaassociated with relatively shorter lengths. Since field pole member 352has wider dimensions in upper half 312 than lower half 311, upper half312 can provide for more units of area. In particular, lower half 311 isassociated with fewer units of area than upper half 312 as field polemember 352 has narrower dimensions in lower half 311. As there are moreunits of area in upper half 312, more flux passes through the associatedlengths, including length 308, than passes through lower half 311. Assuch, more flux passes through shorter lengths than the longer lengthsassociated with lower half 311.

In view of the foregoing, field pole member 352 provides for flux pathsthat, on average, are shorter than found in other stator assemblies ofcomparable length along an axis of rotation. Therefore, a total fluxpassing through a pole face passes into a greater quantity of unit areasassociated with relatively shorter flux path lengths than with otherstator assemblies. Note that field pole members depicted in FIG. 3D (andelsewhere herein), such as field pole member 352, are not intended to belimited to field pole members that provide straight flux paths. Rather,field pole member 352 can include structural attributes to provide asubstantially straight flux path (e.g., consecutive segments of fluxpath portions that do not deviate more than 60 degrees).

FIGS. 3E to 3F depict an example of a field pole member configured tointeroperate with inner rotor assemblies, according to some embodiments.As shown, FIGS. 3E and 3F depict field pole member 356 being aninwardly-facing field pole member with a pole face being oriented in adirection toward an axis of rotation 345. A pole face 354 a is shown toinclude a number of unit areas each associated a length between polefaces 354 a and 354 b of FIG. 3F. Note that the units of area in FIG. 3Eare not drawn to scale and each is equivalent to the other unit areas.Pole face 354 a includes a unit area 324 and a unit area 326. In FIG.3F, unit area 324 is associated with a length 319 between unit area 324of pole face 354 a and unit area 325 of pole face 354 b. Similarly, unitarea 326 is associated with a length 318 between unit area 326 of poleface 354 a and unit area 327 of pole face 354 b. Length 318 isrelatively shorter than length 319. As such, flux passing over length318 has a relatively shorter flux path than if the flux passed overlength 319. Each unit area of pole face 354 a is associated with alength extending to another unit area of pole face 354 b.

As with field pole member 352 of FIGS. 3C and 3D, field pole member 356can be characterized by a mean or average length per unit area, whichcan be determined by adding the lengths associated with each of the unitareas and dividing the sum by the number of unit areas in pole face 354a. The average length per unit area is indicative of the amount ofmaterial within field pole member 356. Again, flux extending along acertain average length per unit experiences less losses than a longeraverage length per unit area. When pole face 354 a confronts a magneticregion (e.g., of a conical magnet, a conical inner rotor assembly, orthe like) that produces a flux density over the surface area of poleface 354 a, a total flux passes via an air gap (not shown) through fieldpole member 356. Another characteristic of field pole member 356 is thatif pole face 354 a is divided axially into two equal halves (i.e., anupper half 321 and a lower half 322) along the axis, then upper half 321is associated with more units of area as field pole member 356 (e.g.,field pole member 356 has wider dimensions in upper half 321 thatinclude more units of area). Lower half 322 is associated with fewerunits of area as field pole member 356 is narrower in lower half 322. Asthere are more units of area in upper half 321, more flux passes throughthe associated lengths, including length 319, than passes through lowerhalf 322. As such, more flux passes through longer lengths than theshorter lengths associated with lower half 322. In some cases, when theaxial length, L, of field pole member 356 of FIG. 3F is equivalent tothe axial length, L, of field pole member 352 of FIG. 3D, field polemember 352 has a shorter average length per unit area than field polemember 356 of FIG. 3F. As such, field pole member 352 may include alesser amount of material than field pole member 356, and may, at leastin some cases, experience less losses.

FIG. 3G depicts field pole members for outer rotor assemblies and innerrotor assemblies, according to some embodiments. Active field polemember 341 includes a coil 331 disposed on a field pole member 328,whereas active field pole member 329 includes a coil 333 disposed aboutfield pole member 336. Active field pole members 341 and 329 can haveequivalent lengths. Active field pole member 341 includes areas 335between coil 331 and the pole faces. Similarly, active field pole member329 includes areas 337 between coil 333 and the pole faces. Areas 335and areas 337 are located at or adjacent to the perimeter of statorassemblies that include active field pole member 341 and active fieldpole member 329, respectively. An example of such a perimeter isperimeter 651 for stator assembly 640 in FIG. 6B. Consequently, areas335 and areas 337 of FIG. 3G, in some examples, are located at oradjacent to motor cases that can be made of either of magneticallypermeable material or electrically-conductive material, or a combinationthereof. When coil 331 is energized, magnetic flux passes through fieldpole member 328 on flux path 338, whereas when coil 333 is energized,magnetic flux passes through field pole member 336 on flux path 339. Asthe areas 335 are lesser in size than areas 337, areas 335 of activefield pole member 341 can have a reduced possibility to generatemagnetic linkage paths 343 (e.g., from one area 337 to another area 337)that otherwise might pass through a surface 347 of a motor case andgenerate losses due to such magnetic linkage paths 343. Therefore, ifthe motor case is composed of magnetically permeable material, areas 335of active field pole member 328 provide for reduced hysteresis lossesrelative to the hysteresis losses produced by magnetic linkage paths 343passing through surface 347 of the motor case. Or, if the motor case iscomposed of electrically-conductive material, areas 335 of active fieldpole member 328 provide for reduced eddy current losses relative to theeddy current losses produced by magnetic linkage paths 343 passingthrough surface 347 of the motor case. In some embodiments, the motorcase can be composed of neither magnetically permeable material norelectrically-conductive material. Note that outer rotor assemblies 353,which are depicted in dashed lines, intercept magnetic flux emanatingfrom pole faces 349 a and prevent such flux from reaching a motor case(not shown). Note further that pole faces 349 a of field pole member 328and pole faces 349 b of field pole member 336 can have surfaces that areoriented at an equivalent acute angle (e.g., 40 degrees) with respect toan axis of rotation.

FIG. 3H depicts an example of a rotor structure implementing anarrangement of offset outer rotor assemblies, according to someembodiments. Rotor structure 370 is shown to include rotor assemblies380 x and 380 y disposed on an axis of rotation 371. Rotor assembly 380x is shown to include magnetic regions 379, which, in turn, can includemagnets and/or magnetic material 382 x (or portions thereof) andmagnetically permeable structures 384 x. Rotor assembly 380 y alsoincludes magnetic regions (not shown) similar to magnetic regions 379,which, in turn, can include magnets and/or magnetic material 382 y (orportions thereof) and magnetically permeable structures 384 y. As rotorassemblies 380 x and 380 y each can contribute to a detent torque whenpositioned to interact with field poles (not shown) in the stator, fluxfrom either rotor assemblies 380 x or 380 y, or both, can contribute todetent. Flux waveforms depicting detent produced in association withrotor assemblies 380 x and 380 y can be substantially similar in shapeand amplitude to each other, and, as such, the amplitudes of the detentwaveforms rotor assemblies 380 x and 380 y can be added together (e.g.,through the principles of superposition). The detent waveforms can addtogether to form a composite detent waveform. As shown, rotor assemblies380 x and 380 y are outer rotor assemblies.

According to at least some embodiments, rotor assemblies 380 x and 380 ycan be offset from each other relative to, for example, a shaft (notshown) coextensive to axis of rotation 371. Rotor assemblies 380 x and380 y can be offset by an angle A to provide for a composite detentwaveform that has an amplitude less than if there was no offset. In someexamples, angle A can be determined to offset at least one detentwaveform to be out of phase (or substantially out of phase), where angleA can be any number of degrees. In at least some examples, angle A canbe any angle between 0 to 30 degrees. A composite detent waveform canhave a reduced amplitude, with the offset rotor assemblies 380 x and 380y causing the detent waveforms to be offset relative to each other. Insome cases, offset detent waveforms can cancel (or substantially cancel)each other for enhanced position control of a motor and relativelysmoother operation, according to various embodiments.

Angle A can be referenced in relation to the rotor assemblies and/orbetween any points of reference associated with the rotor assemblies,and can be expressed in terms of mechanical degrees about axis 371. Inat least some embodiments, angle A is an angle between poles for rotorassemblies 380 x and 380 y, such as an angle between one pole associatedwith rotor assembly 380 x and another pole associated with rotorassembly 380 y. For example, a south pole associated with rotor assembly380 x can be positioned on axis 371 at an angle A relative to a northpole associated with rotor assembly 380 y. In at least some embodiments,angle A can be referenced relative to a first reference point associatedwith rotor assembly 380 x and a second reference point associated withrotor assembly 380 y. As shown in this example, reference points, suchas reference points 399 a and 399 b of associated magnetic regions 379,can be used to determine an offset from each other by angle A. In somecases, reference points 399 a and 399 b each can represent a point alonga line or plane that bisects the surface of either magneticallypermeable structure 384 w or magnetically permeable structure 384 z.Reference points can include other points of reference, such as a pointon a common edge or side (e.g., adjacent to a magnet, such as magnet 382x or magnet 382 y). According to at least some embodiments, rotorassemblies 380 x and 380 y can be offset relative to planes includingreference points, where each of the reference points is located in aplane that includes axis 371. As shown, a ray 374 y extending out fromrotor assembly 380 y can be offset from another ray 374 x oriented intorotor assembly 380 x. In particular, a plane 372 a including ray 374 x(e.g., into magnetically permeable structure 384 w) can be offset by anangle A from another plane 372 b that includes ray 374 y (e.g.,extending out from magnetically permeable structure 384 z). While planes372 a and 372 b including rays 374 x and 374 y can include axis ofrotation 371, the planes need not be so limited. Plane 372 b bisectsmagnetically permeable material 384 z such that reference point 399 b islocated at midpoint between equal arc lengths 398 a and 398 b (e.g.,along a circle centered on axis of rotation 371). Note that structuralfeatures, such as feature 377, which is shown with shading, is optionaland need not be present in various examples.

FIGS. 4A and 4B depict different perspective views of an example of anouter rotor magnet or rotor assembly, according to some embodiments. InFIG. 4A, a rotor assembly 400 includes magnetic material 482 (e.g., aspermanent magnets) having surfaces 483 configured to confront polefaces, and magnetically permeable structures 484 having surfaces 485that are configured also to confront pole faces. Surfaces 483 and 485can specify a magnetic region and/or a pole for rotor assembly 400. Notethat while surfaces 483 of magnetic material 482 are configured toconfront pole faces, flux need not, according to some embodiments, passthrough surfaces 483. Rather, the flux and/or flux density produced bythe structures of magnetic material 482 can magnetically couple to(i.e., form flux paths through) the sides of magnetically permeablestructures 484, whereby flux produced by the structures of magneticmaterial 482 can interact via surfaces 485 with pole faces.

FIG. 4B depicts another perspective view of a rotor assembly 450includes magnetic material 482 (e.g., as permanent magnets), andmagnetically permeable structures 484. A surface 485 a of magneticallypermeable structures 484 a can be at angle “A” from centerline 472passing through the center of rotor assembly 450, where line 470 iscoextensive with at least a portion of surface 485 a. Further, surfaces483 a of magnetic material 482 a can be at angle “A” (or any otherangle) from centerline 472. In some embodiments, centerline 472coincides with an axis of rotation. Centerline 472 can represent ageometric center of a number of cross-sections of rotor assembly 450 inplanes perpendicular to the axis of rotation. To illustrate, FIG. 4Bdepicts a cross section 486 having an annular or a disc shape that iscentered on centerline 472, with cross section 486 residing a planeperpendicular to centerline 472. Further, centerline 472 can represent,for example, a line about which rotor assembly 450 is symmetric. In atleast some embodiments, surfaces 485 a are used to form air gaps withadjacent pole faces (not shown). In at least one example, surfaces 485,such as surface 485 a, are configured to be coextensive with portions ofan outer surface of a cone, whereas surfaces 483, such as surface 483 a,may or may not be configured to be at angle A or coextensive with theouter surface of a cone. Thus, flux paths may pass between surfaces 485and the pole faces, whereas flux paths need not exist between surfaces483 and the pole faces.

FIGS. 4C and 4D depict a front view and a rear view of an example of anouter rotor assembly, according to some embodiments. FIG. 4C depicts afront view of a rotor assembly 480 including an arrangement of magneticregions 440. A magnetic region 440 includes surface portion 483 a,surface portion 483 b, and surface 485 associated with respectivemagnetic material 482 a, magnetic material 482 b, and magneticallypermeable structure 484, whereby surfaces 483 a, 485, and 483 b areconfigured to confront pole faces (not shown). Magnetic regions 440 arearranged radially about a centerline 470. Further to FIG. 4C, the frontview (e.g., the view in which at least surface 485 confronts pole facesof field pole members) of magnetically permeable structure 484 a is acircular sector shape (e.g., a “pie piece”-like cross-section in a planesubstantially perpendicular to the axis of rotation). In the exampleshown, magnetically permeable structure 484 a can be defined as aportion of a circle enclosed by line 471 a and line 471 b originatingfrom, for example, a point 477, and bounded by a first arc or lineassociated with an outer radius 473 a and a second arc or lineassociated with an inner radius 473 b. Line 471 a and line 471 b can bea first boundary and a second boundary extending from a point 477, whichis a center of a circle (not shown) offset from centerline 470. Notethat inner radius 473 b can be relatively constant in an extensionportion (e.g., in an extension region 426 of FIG. 4E) and can vary in anangled surface portion (e.g., in an angled surface portion 428 of FIG.4E) along the axis of rotation.

Referring back to FIG. 4C, the front view of magnetic material 482, suchas magnetic material 482 c, indicates that sides 475 a and 475 b ofmagnetic material 482 can be parallel to each other. Further, magneticmaterial 482 c can also be bound by an arc or line associated with anouter radius 473 a and another arc or line associated with an innerradius 473 b. Note that the shapes of magnetically permeable structures484 and magnetic materials 482 a and 482 b are not limited to thoseshown and can be of any shape. For example, magnetic materials 482 a and482 b can be wedge-shaped (not shown) and the shapes of magneticallypermeable structures 484 can be dimensioned to have parallel sides, suchas sides 475 a and 475 b. Note that sizes (e.g., relative sizes) ofmagnetically permeable structures 484 and magnetic materials 482 a and482 b are not limited to those depicted in this and other figures. Also,rotor assembly 480 and other variations thereof need not be limited tomagnetically permeable structures 484 and magnetic materials 482 a and482 b, but may include other materials, structures and/or arrangementsof magnetically permeable structures 484 and magnetic materials 482 aand 482 b.

FIG. 4D depicts a rear view 490 of a rotor assembly 480 includingarrangements of magnetic material 482 a, magnetic material 482 b, andmagnetically permeable structures 484 of FIG. 4C, where magneticmaterial 482 a, magnetic material 482 b, and magnetically permeablestructures 484 are used to form a magnetic region. Surfaces 489 a, 487,and 489 b are rear surfaces of magnetic material 482 a, magneticallypermeable structure 484, and magnetic material 482 b, respectively. Insome embodiments, the cross-sections of magnetic material 482 a and ofmagnetic material 482 b are substantially rectangular in a planeperpendicular to centerline 470. In various instances, one or more ofthe surfaces of either the magnetic material or the magneticallypermeable structure can be curved or straight (or can be formed frommultiple straight portions to approximate a curved surface) at an innerradius dimension, such as at inner radius 473 b of FIG. 4C or an outerradius dimension, such as at an outer radius 473 a of FIG. 4C. Thecross-section of magnetically permeable structure 484 can be trapezoidalin shape (e.g., wedge-shaped) in a plane perpendicular to centerline470. Further, FIG. 4D depicts a rear view of structures for formingmagnetic poles 460 and 462, where pole 460 is a north pole and pole 462is a south pole. In the example shown, a portion (“N”) 482 g of magnet482 c, a portion (“N”) 482 h of magnet 482 d and magnetically permeablestructure 484 c form pole 460, whereas a portion (“S”) 482 j of magnet482 d, a portion (“S”) 482 k of magnet 482 e, and magnetically permeablestructure 484 d form pole 462. Note that magnets 482 c, 482 d, and 482 ecan be polarized in the direction shown by the flux arrows with north(“N”) and south (“S”) notations, whereby the directions of polarizationcan be circumferential (or substantially circumferential), and, thus,can be tangent (or substantially tangent) to a circle (not shown) aboutcenterline 470. In some examples, the directions of polarization can becircumferential in that flux passes generally of, at, or near thecircumference of a circle (not shown) about a centerline and/or an axisof rotation. In some embodiments, the portions of magnets 482 a to 482 bneed not be visible in the rear view. For example, the axial lengths ofmagnets 482 of FIGS. 4A and 4B need not extend along centerline 472 aslong as magnetically permeable material 484.

FIGS. 4E to 4G depict cross-sectional views of an example of an outerrotor assembly, according to some embodiments. Diagram 420 of FIG. 4Eincludes a cross-section of an outer rotor assembly in which a plane(“X-X′”) bisects the outer rotor along or through the axis of rotation412. The cross-section includes an extension portion 426 and an angledsurface portion 428 having at least a subset of dimensions along theaxis of rotation 412. Extension portion 426 includes an inner radius(“IR”) 421 as a dimension that is substantially constant along axis ofrotation 412. Extension portion 426 can be configured to vary an amountof flux passing through a surface of magnetically permeable structure,such as surface 425. The amount of flux can be varied by modifying adimension along the axis, such as an axial length 429. The amount offlux can be generated at least by magnetic material. In some examples,the amount of flux can be varied by modifying another dimension, height427, which can be perpendicular to axis of rotation 412. In some cases,modifying the outside radius (“OR”) 499 of the outer rotor assembly mayinfluence height 427 to modify the amount of flux. Also, modifyingheight 427 to modify the amount of flux may or may not influence outsidediameter 499. Angled surface portion 428 is shown to have surfaces atmultiple radial distances 423 from axis of rotation 412, whereby radialdistances 423 increase at axial distances further from extension portion426 along axis of rotation 412. But note that radial distances 423 neednot vary in some cases (not shown). For example, one or more subsets ofradial distances can be constant or substantially constant for one ormore subsets or ranges of lengths along the axis of rotation. As shown,the interior portions of an internal permanent magnet (“IPM”) and/orportions of the magnetically permeable material and magnetic materialare disposed at radial distances greater than a radial distance 423 fromthe axis of rotation.

In some embodiments, the portions of magnets 482 a to 482 b need not bevisible in the rear view. For example, the axial lengths of magnets 482of FIGS. 4A and 4B need not extend along centerline 472 as long asmagnetically permeable material 484 along the axis of rotation. Thus,magnets 482 can be embedded in magnetically permeable material such thatthey need not extend axially through the axial length of a rotorassembly. In some embodiments, magnets 482 having a shorter axial lengththan magnetically permeable material 484 can be disposed adjacentsupplemental structures 431 that can include any material, such asplastic. In some instances, supplemental structures 431 can include anymaterial that reduces or prevents magnetic short-circuits betweenstructures of magnetically permeable material 484. While magnets 482 maybe disposed in angled surface portion 428, they can be disposed in aportion of an extension portion or can be omitted therefrom. In someembodiments, surfaces 483 of magnets 482 can be covered by magneticallypermeable material between surfaces 483 and respective air gaps and/orpole faces.

Diagram 410 of FIG. 4F is a perspective view of a cross-section of anouter rotor assembly 432 in which a plane (“X-X′”) 411 bisects the outerrotor assembly along the axis of rotation 412, according to at least oneembodiment. The inner diameter of extension portion 426 can include oneor more radial distances. In the example shown, the inner diameter caninclude as radial distances 413 and 414 between axis of rotation 412 andthe surfaces in extension portion 426 for magnets 482 and magneticallypermeable structure 484. In some cases, radial distances 413 and 414 canbe the same.

Diagram 430 of FIG. 4G is another perspective view of a cross-section ofan outer rotor assembly 432, according to at least one embodiment. Asshown, the surfaces of magnets 482 and magnetically permeable structures484 can be at the same or at different distances from the axis ofrotation (e.g., the surfaces for magnets 482 and magnetically permeablestructure 484 can reside on the same or different interior or exteriorsurface portions of a cone). Thus, surfaces 437 of magneticallypermeable structures 484 and surfaces 439 of magnets 482 can bedimensioned similarly or differently. In the particular example shown,surfaces 437 of magnetically permeable structures 484 can be disposed ata radial distance 433 from an axis of rotation, whereas surfaces 439 ofmagnets 482 can be disposed at a radial distance 435 from the axis ofrotation. Note that in at least some embodiments, surfaces 437 ofmagnetically permeable structures 484 are configured to convey fluxbetween a pole face (not shown) and outer rotor assembly 432 in anangled surface portion. Thus, surfaces 439 of magnets need not becoextensive with the same conically-shaped space to which surfaces 437are coextensive. Rather, surfaces 439 of the magnets can be described asbeing “recessed” relative to surfaces 437. As air gaps can be defined inassociated with surfaces 437 of magnetically permeable structures 484,the distances 435 can be equal or greater than distances 433 relative toan axis of rotation. Further, surfaces 439 can be of any shape are notlimited to the shapes shown in FIG. 4G.

FIGS. 5A and 5B depict different views of an example of a statorassembly, according to some embodiments. FIG. 5A is a diagram 500depicting a side view of stator assembly 540 including an arrangement ofactive field pole members each including a field pole member 510 havingpole faces 514 a and 514 b, and a coil 512. As shown, pole faces 514 aand portions of respective pole shoes are disposed in a portion 513 a ofstator assembly 540 and pole faces 514 b are disposed in a portion 513 bof stator assembly 540. Pole faces 514 b and portion 513 b areconfigured to extend into an interior region 524 of a rotor assembly540. According to some embodiments, interior region 524 is an opening,space or cavity configured to receive portion 513 b, and can be formedas having a frustum shape. As is known, a frustum is a cone-based shapewith a first circular base (e.g., a bottom base) and a second circularbase (e.g., a top base), whereby the second base is formed by cuttingoff the tip of a cone along a plane perpendicular to the height of acone. The height (not shown) of the cone in this example lies along axisof rotation 520. Interior region 524 can be formed by planes 533 and 535passing perpendicular to an axis of rotation 520. Planes 533 and 535pass or cut through a conical boundary 515 of a cone disposed on an axisof rotation 520, with apex 511 b of the cone lying on axis of rotation520. In at least one example, planes 533 and 535 can form a first baseand a second base, respectively, of a frustum-shaped interior region524. Conical boundary 515 is oriented so as to extend from apex 511 b toenclose another point 511 a on axis of rotation 520 within the interiorof conical boundary 515. Point 511 a can serve as another apex for aconical boundary (not shown) to enclose portion 513 a within. An angledsurface 525 of, for example, a magnetic region of rotor assembly 540 isdisposed within region 523 that is external to the conical boundary 515,whereas pole faces 514 b reside in region 521 that is internal to theconical boundary 515. Further, pole faces 514 b can be oriented at anangle relative to axis of rotation 520, whereby the angle is the same ordifferent relative to an angle coextensive with angled surface 525.

FIG. 5B is a diagram 550 depicting a side view of stator assembly 580including an arrangement of active field pole members each including afield pole member 510 having pole faces 514 a and 514 b, and a coil 512.Coil 512 can be disposed on or over a bobbin 516. As shown in FIGS. 5Aand 5B, pole faces 514 a and 514 b are configured to align with a lineor surface that is at an angle with, for example, the axis of rotation.Further, pole faces 514 a and 514 b include surfaces (or portionsthereof) are contoured to also align with or be bounded by the line orthe surface at the above-mentioned angle. Therefore, pole faces 514 aand 514 b can include convex surface portions. According to someembodiments, pole faces 514 a and 514 b can be substantially flat orflat. A substantially flat or flat surface for a pole face can becoextensive with at least one or more portions of a conically-shapedspace. In one example, a width of a pole face from the group of polefaces 514 a and 514 b can be or can substantially be coincident with anarc on a circle centered on the axis of rotation. The width of the poleface can decrease as, for example, the number of field pole membersincrease for stator assemblies 540 of FIGS. 5A and 580 of FIG. 5B. Thewidth decreases as the arc makes up a smaller portion of the diameter ofthe circle, and as the arc is reduced, the arc approximates a line bywhich the surface of the pole face can be bounded.

FIG. 6A depicts an outer rotor assembly and a stator assembly configuredto interact with each other, according to some embodiments. Outer rotorassembly 630 and stator assembly 640 can interact with each other whenarranged co-linearly. Diagram 600 depicts rotor assembly 630 includingmagnets 632 and magnetically permeable structures 634. Rotor assembly630 is configured to center on a centerline 602 b, which can coincidewith an axis of rotation. Surface 683 and surface 685 of respectivemagnets 632 and magnetically permeable structures 634 can be coextensivewith or can be bounded by a line 670 or surface oriented at an angle, A,from centerline 602 b. In some embodiments, surfaces 685 of magneticallypermeable structures 634 need only be oriented at angle A for formingair gaps with pole faces 614, with surfaces 683 being optionallyoriented with angle A. Stator assembly 640 is shown to include a subsetof pole faces 614, with the dimensions of a number of field pole membersestablishing a perimeter 651 for stator assembly 640. The dimensions ofthe number of field pole members can also establish a diameter 657, asshown in FIG. 6B. Referring back to FIG. 6A, an envelope 642 can defineone or more boundaries in which pole faces 614 (or surface portionsthereof) are oriented, with envelope 642 being centered on a center line602 a. In some cases, envelope 642 is a conically-shaped threedimensional space that can circumscribe the surfaces of pole faces 614.The interior surface of envelope 642 can be coincident with at least oneangle, B. Note that angle B can be the same as angle A, or can varytherefrom (e.g., an air gap can have a uniform radial thickness or canhave a variable axial thickness that varies in thickness along theaxis). Stator assembly 640 can also be centered on centerline 602 a.Centerlines 602 a and 602 b can be coincident with an axis of rotation,at least in some cases. Note that while envelope 642 can define aboundary of pole faces 614, the pole faces need not be contoured orconvex in all examples. For example, pole faces 614 can include flatportions that are oriented at angle B within the boundary set forth byenvelope 642.

FIGS. 6B to 6C depict cross-sections of field pole members fordetermining a surface area of a pole face, according to someembodiments. Angles A and/or B of FIG. 6A can be determined as follows.Generally, a rotor-stator structure is designed based on spatialconstraints, such as a volume into which the rotor-stator structure isto reside. Thus, stator assembly 640 of FIG. 6A can be configured tohave a perimeter 651 and/or a diameter 657. FIG. 6B depicts across-section 650 in a plane perpendicular to axis of rotation 656 withactive field pole members arranged as a stator assembly within perimeter651. Cross-section 650 can be located within a coil region 644 of FIG.6A in which coils are disposed axially (e.g., the coils can be wound inan axial direction to generate ampere-turn (“AT”) flux in a directionalong an axis of rotation 656 of FIG. 6B within the field pole membersin coil region 644. Active field pole members include coils 652 andfield pole members 654 of FIG. 6B. A desired amount of flux (e.g., atotal amount of flux) can be determined in coil region 644 within anactive field pole member to produce a value of torque. A flux densityproduced at an air gap can be influenced by the magnetic material usedfor magnets 632 (e.g., neodymium magnets produce greater flux densitiesthan, for instance, a ceramic magnet). Therefore, a specific magneticmaterial can be selected to produce a flux density to achieve a desiredamount of flux in a portion of a field pole member having across-sectional area 665 of FIG. 6C, which depicts a cross-section 660.Cross-sectional area 665 can provide for the desired amount of flux(e.g., total flux composed of at least AT-generated flux and magneticmaterial-generated flux) through the field pole member. In some cases,cross-section 660 can be perpendicular to centerline 602 a of FIG. 6A.For example, cross-section 660 can be depicted as cross-section 661 of afield pole member 641 of stator assembly 640 of FIG. 6A, withcross-section 661 being in a plane (not shown) perpendicular tocenterline 602 a.

FIG. 6D illustrates a surface area of a pole face determined as afunction of the flux in a coil region and/or the flux density producedby at least one magnetic region, the surface area being oriented atangle from a reference line, according to some embodiments. Surface area694 of a pole face 614 of FIG. 6A can be based on the flux in coilregion 644 and the flux density produced by at least one magnet 632 ofthe magnetic region, either (or both) of which can influence thegeneration of a desired amount of torque. Therefore, surface area 694can be determined as a function of flux produced by the magneticmaterial of magnets 632, the flux originating tangent to a circle aboutcenterline 602 a (i.e., as determined by the direction of polarization).Angle B can be determined to achieve surface area 694. Note that surfacearea 694 is greater than cross-sectional area 665, thereby enhancing theconcentration of magnet-produced flux within the field pole member. Poleface 614 a is oriented at an angle B (e.g., an acute angle to centerline602 a) to establish surface area 694. Note that the depiction in FIG. 6Dis viewed from a point on a line normal to the surface of pole face 614a. In some cases, at least a portion of pole face 614 a is coextensivewith a portion of a cone. Angle A can be determined to orient thesurface 685 of at least magnetically permeable structure 684 to the axisof rotation to form the air gap.

FIG. 7 depicts a cross-section of a rotor-stator structure in whichfield pole members are positioned adjacent to magnetic regions to formair gaps, according to some embodiments. Cross-section 700 includesfield pole members 710 a, 710 b, and 710 c oriented between portions ofouter rotor assemblies. In particular, field pole member 710 a islocated between magnetic region 790 a and magnetic region 790 b. An airgap 711 is formed between magnetic region 790 a and a pole face (notshown) of field pole member 710 a and another air gap 713 is formedbetween magnetic region 790 b and another pole face (not shown) of fieldpole member 710 a. Magnetic region 790 a includes magnets 732 a (orportions thereof) and a magnetically permeable structure 734 a, andmagnetic region 790 b includes magnets 732 b (or portions thereof) and amagnetically permeable structure 734 b. In operation, a flux path (or aportion thereof) can extend from magnetic region 790 a via field polemember 710 a to magnetic region 790 b in examples where magnetic region790 a forms a north pole and magnetic region 790 b forms a south pole.In this example, magnets 732 a (or portions thereof) include north polesoriented toward magnetically permeable structure 734 a and magnets 732 b(or portions thereof) include south poles oriented in a direction awayfrom magnetically permeable structure 734 b. Note that while magneticregions 790 a and 790 b are shown to be offset, they need not be.

FIG. 8A depicts cross-sections of rotor-stator structure portionsillustrating one or more flux path examples, according to someembodiments. Diagram 800 includes field pole members 810 a, 810 b, and810 c disposed between rotor assemblies 830 a and 830 b. As shown, fluxpath portion 891 a can extend through field pole member 810 a frommagnetically permeable structure 834 a in rotor assembly 830 a tomagnetically permeable structure 834 b in rotor assembly 830 b. Fluxpath portion 891 a also passes through air gaps 711 and 713 that areformed between field pole member 810 a and respective rotor assemblies830 a and 830 b. Magnetically permeable structure 834 b and magnets 832a and 832 c (or portions thereof) are shown as constituting magneticregion 890 e, which forms a south (“S”) pole. The flux path portionpasses from magnetic region 890 e to magnetic region 890 d, which formsa north (“N”) pole. Magnetically permeable structure 834 c and at leastmagnet 832 a (or a portion thereof) are shown as constituting magneticregion 890 d. The flux exits rotor assembly 830 b as flux path portion891 b and passes through field pole member 810 b before enteringmagnetically permeable structure 834 d of magnetic region 890 a (i.e., asouth pole), which also includes at least magnet 832 b. The flux passesto magnetic region 890 b (i.e., a north pole) composed of magneticallypermeable structure 834 a and magnets 832 b and 832 d (or portionsthereof), thereby establishing a closed flux path. According to theexample shown, rotor assemblies 830 a and 830 b and field pole members810 a and 810 b form a closed flux path. Portions of the closed fluxpath pass through at least field pole members 810 a and 810 b and atleast rotor assemblies 830 a and 830 b in opposite directions or insubstantially opposite directions. In some cases, a first portion of theclosed flux path can pass through rotor assembly 830 a in asubstantially opposite direction than a second portion of the closedflux path that passes through rotor assembly 830 a. For example, thefirst portion of the close flux path can pass through rotor assembly 830a in one direction about the axis of rotation (e.g., clock-wise) and thesecond portion of the close flux path can pass through rotor assembly830 b in another direction about the axis of rotation (e.g., counterclock-wise).

In a specific embodiment, the rotor-structure can be configured suchthat flux path portion 891 a can separate in rotor assembly 830 b toform flux path portion 891 b and flux path portion 891 c. Flux pathportion 891 b passes through field pole member 810 b, whereas flux pathportion 891 c passes through field pole member 810 c. The flux frommagnetic region 890 e enters magnet region 890 f (i.e., a north pole)including magnetically permeable structure 834 e and at least magnet 832c (or a portion thereof). The flux exits rotor assembly 830 b and passesthrough field pole member 810 c and into magnetic region 890 c (i.e., asouth pole) of rotor assembly 830 a. Magnetic region 890 c includesmagnetically permeable structure 834 f and at least magnet 832 d (or aportion thereof). Note that the generation of flux path portion 891 c isoptional and need not be present in each rotor-stator structure of thevarious embodiments. Note, too, a “flux path portion” need not belimited to those shown, but can be any part of a flux path and of anylength.

FIG. 8B depicts cross-sections of rotor-stator structure portionsillustrating specific flux path examples, according to some embodiments.Similar to FIG. 8A, diagram 850 includes field pole members 810 a, 810b, and 810 c disposed between rotor assemblies 830 a and 830 b. Aprincipal flux path (or portions thereof) is shown to traversecircumferentially through one magnet in a subset of magnets in rotorassembly 830 a and circumferentially through another magnet in anothersubset of magnets in rotor assembly 830 b. According to someembodiments, a principal flux path passes through magnets in rotorassemblies that generally provide a predominant amount of flux (e.g.,magnet-produced flux), thereby contributing predominantly to fluxproduction (e.g., torque production) relative to other magneticmaterial, such as boost magnets, which are describe below. Toillustrate, consider that a principal flux path (or portions thereof)passes from a point 820 associated with magnetically permeable material834 d through magnet 832 b to point 821 associated with magneticallypermeable material 834 a in rotor assembly 830 a. The principal fluxpath can include flux path portion 891 a between points 821 and 827, theprincipal flux path traversing axially through field pole member 810 a.In rotor assembly 830 b, the principal flux path (or portions thereof)passes from point 827, which is associated with magnetically permeablematerial 834 b, through magnet 832 a to point 826 associated withmagnetically permeable material 834 c. The principal flux path caninclude flux path portion 891 b between points 826 and 820, theprincipal flux path traversing axially through field pole member 810 b,thereby forming a closed flux path. Another principal flux path is shownto include flux path portions that traverse circumferentially from point823 through magnet 832 d (e.g., as one magnet in a subset of magnets) topoint 822 in rotor assembly 830 a, and from point 828 through anothermagnet 832 c (e.g., in another subset of magnets) to point 829 in rotorassembly 830 b.

FIG. 8B also shows a flux path (or portions thereof) that omits orbypasses magnets 832 b and 832 d in rotor assembly 830 a and magnets 832a and 832 c rotor assembly 830 b. The flux path traverses predominantlyin a circumferential direction that bypasses a magnet in a subset ofmagnets in either rotor assembly 830 a or rotor assembly 830 b. Considerthe following example in which a flux path (or portions thereof) passesfrom a point 820 via point 861 to point 821 in rotor assembly 830 a,thereby bypassing magnet 832 b. Point 861 represents a point associatedwith a structure 813 a that is configured to boost an amount of fluxpassing along, for example, path portion 891 a. Structure 813 a can alsobe configured to provide a magnetic return path. The flux path can thenpass axially between points 821 and 827 through field pole member 810 a.In rotor assembly 830 b, the flux path (or portions thereof) passes frompoint 827 via a structure 813 b including point 863 to point 826. Theflux path passes from point 826 to point 820, thereby forming a closedflux path. Another flux path (or portions thereof) is shown to includeflux path portions passing from a point 828 via a structure 813 dincluding point 864 to point 829 in rotor assembly 830 b, and from point823 via a structure 813 c including point 862 to point 822 in rotorassembly 830 a. Note that structures 813 a, 813 b, 813 c, and 813 d caninclude the same or different elements and/or compositions.

FIG. 8C is a diagram depicting elements of a structure for a rotorassembly, according to some embodiments. Diagram 851 includes rotorassembly 830 a, as described in FIGS. 8A and 8B, and a structure 813 a.Structure 813 a is configured to boost an amount of flux passing along aflux path and to provide a magnetic return path. Further, structure 813a can re-orient that direction of flux passing between points 820 and821. For example, absence of structure 813 a causes flux to pass betweenpoints 820 and 821 in a direction opposite than depicted by the arrow(i.e., in a direction from point 821 (“N”) to point 820 (“S”)). In theexample shown, structure 813 a includes magnetic material, such asmagnets 816 a and 816 b, and/or a flux conductor shield that provides amagnetic return path and shields external regions from being exposed tostray flux. A flux conductor shield can include magnetically permeablematerial that, in some cases, can be equivalent to that of field polemembers 810 a to 810 c of FIGS. 8A and 8B. Referring back to FIG. 8C,the directions of polarization for magnets 816 a and 816 b influence thedirection of flux traveling between points 820 and 821. In variousembodiments, magnets 816 a and 816 b can represent axial boost magnetsor radial boost magnets (e.g., either inner radial boost magnets orouter radial boost magnets).

FIGS. 9A to 9C depict cross-sections of a rotor-stator structure portionillustrating examples of one or more flux path portions, according tosome embodiments. Diagram 900 depicts cross-sections of field polemembers 910 a and 910 c that are disposed between rotor assemblies 930 aand 930 b. As shown, cross-section X-X′ is a cross-section of field polemember 910 a between rotor assemblies 930 a and 930 b, wherecross-section X-X′ is a medial plane extending in an axial directionthrough a south magnetic pole including a magnetically permeablestructure (“S”) 922 a and a north magnetic pole including a magneticallypermeable structure (“N”) 920 a. The medial plane divides field polemember 910 a approximately in half (e.g., includes percentages from50/50 to 60/40 on either side). Similarly, cross-section Y-Y′ is across-section of field pole member 910 c between rotor assemblies 930 aand 930 b, where cross-section Y-Y′ is also a medial plane extending inan axial direction through a north magnetic pole including amagnetically permeable structure (“N”) 920 b and a south magnetic poleassociated with another magnetically permeable structure (“S”) 922 b.Cross-section Y-Y′ divides field pole member 910 c approximately inhalf.

FIG. 9B depicts a cross-section (“X-X′”) 901 of field pole member 910 ain which a flux path portion 991 extends between cross-sections of rotorassemblies 940 a and 940 b that correspond to magnetically permeablematerials 922 a and 920 a, respectively. In some embodiments, field polemember 910 a is configured to provide that flux path portion 991 passesthrough a portion 904 of field pole member 910 a that is located at oneor more distances farther than other portions of field pole member 910a, such as a portion 905, from a reference line (e.g., an axis ofrotation). Portion 904 of field pole member 910 a can have an axiallength that is shorter than other portions of field pole member 910 a.For example, one or more laminations disposed within portion 904 canhave lengths that are shorter than the lengths of laminations that aredisposed in other portions of field pole member 910 a. Note that a point962 on the surface of the magnetically permeable structure in thecross-section of rotor assembly 940 a can be at a radial distance 996from a reference line 999 (e.g., the axis of rotation) and a point 964on the pole face can be at a radial distance 994 from reference line999, wherein the both points 962 and 964 can lie in a plane 960, which,for example, can be perpendicular to reference line 999. In outer rotorassemblies, radial distance 996 is greater than radial distance 994.

FIG. 9C depicts a cross-section (“Y-Y′”) 903 of field pole member 910 cin which a flux path portion 993 extends between cross-sections of rotorassemblies 942 a and 942 b. In some embodiments, field pole member 910 cis configured to provide that flux path portion 993 passes through aportion 906 of field pole member 910 a similar to flux path portion 991of FIG. 9B. Note that flux path portion 993 can be representative ofeither flux path portion 891 b or 891 c of FIG. 8A, in at least someexamples.

FIG. 10 depicts a view along an air gap formed between a magnetic regionand a pole face, according to some embodiments. Diagram 1000 is a viewof an air gap 1090 along a curved surface (not shown) of, for example, aconically-shaped envelope, whereby the air gap can be coextensive withor located on the curved surface. Further, diagram 1000 also depicts amagnetic region 1040 confronting a pole face of a field pole member1010, where magnetic region 1040 includes magnets 1032 (or portionsthereof) and a magnetically permeable structure 1034. The pole face offield pole member 1010 and magnetic region 1040 (or a portion thereof)establish an air gap 1090. As shown, the surface of the pole faceincludes a curved surface between a side of field pole member 1010 nearone of magnets 1032 and the other side of field pole member 1010 nearanother magnet 1032.

FIGS. 11A to 11C depict various views of a field pole member, accordingto some embodiments. FIG. 11A is a top view of a field pole member 1110that includes pole faces 1114 a and 1114 b, and pole core 1111. Asillustrated, pole face 1114 a includes dashed lines to represent thecontours indicating a convex surface. Note that the dashed linesrepresenting the contours can represent the use of laminations to formfield pole member 1110, and the dashed lines can represent any number oflaminations that can be used to form pole faces 1114 a and 1114 b, aswell as field pole member 1110. FIG. 11B is a perspective view of fieldpole member 1110 including at least a pole face 1114 a, with field polemember 1110 being formed with a stack 1174 of laminations. Line 1170 canrepresent a flux path passing through a portion 1172 of field polemember 1110 shown in FIG. 11C. Portion 1172 is an axial portion orcross-section portion located at a distance from an axis of rotation. Insome embodiments, portion 1172 is an axial portion that has dimensionsto facilitate a reduction in flux density to reduce losses thatotherwise might accompany a higher flux density. FIG. 11C is a diagram1150 showing a cross-section view 1120 and a side view 1130 of fieldpole 1110. Cross-section view 1120 depicts a stack of laminations thatat the lower portions have a width, W2, with the laminations increasingin width up to, for example, width, W1, for the upper portions oflaminations. Cross-section view 1120 can lie in a plane that isperpendicular to the axis of rotation, but it need not (e.g., thecross-section can be perpendicular to the direction of flux generated ina coil region and in the direction of AT flux-generated). In someembodiments, an axial portion 1160 includes, for example, one or morelaminations having a width W1 in a plane perpendicular to the axis ofrotation at a radial distance 1196 (e.g., an average radial distance ofthe radial distances for each of the laminations associated with axialportion 1160) from a reference line 1199 (e.g., the axis of rotation),and an axial portion 1162 can include one or more laminations having awidth W2 can be located at a radial distance 1194 (e.g., an averageradial distance of the radial distances for each of the laminationsassociated with axial portion 1162). Note that in the example shown,radial distance 1196 is greater than radial distance 1194. Further, notethat axial portion 1160 has an axial length 1190 extending between twopole faces 1114 a and 1114 b at approximately at radial distance 1196,and axial portion 1162 has an axial length extending between the twopole faces at approximately radial distance 1194, where axial length1190 is less than the axial length at radial distance 1194. This canfacilitate a reduction in losses that otherwise might accompany longerlaminations. Note that widths W1 and W2 can represent average widths oflaminations or flux conductors in the respective axial portions.

FIG. 12 depicts a magnetic region of a rotor assembly as either a northpole or a south pole, according to some embodiments. Diagram 1200depicts a magnetic region 1240 of a rotor assembly 1230, with magneticregion 1240 (e.g., as shown by the dashed line) including magnets 1232 aand 1232 b and magnetically permeable material 1234. Magnetic region1240 can be configured as either a north pole 1220 or a south pole 1222.North pole 1220 can be implemented as magnetically permeable material1234 with or without magnets 1232 a and 1232 b. As shown, magnets 1232 aand 1232 b can be polarized such that their north poles are orientedtoward or substantially toward the sides of magnetically permeablestructure 1234. In some embodiments, the polarization of magnets 1232 aand 1232 b can be in a direction substantially orthogonal to a lineextending axially between two pole faces of the same field pole member.As shown, the surfaces of magnets 1232 a and 1232 b can be polarized asnorth poles and the flux therefrom enters magnetically permeablematerial 1234 in a manner that surface 1235 is a north pole (or issubstantially a north pole) for rotor assembly 1230. Or, south pole 1222can be implemented as magnetically permeable material 1234 with orwithout magnets 1232 a and 1232 b, with magnets 1232 a and 1232 b havingtheir south poles oriented toward or substantially toward the sides ofmagnetically permeable structure 1234. In some embodiments, thepolarization of magnets 1232 a and 1232 b can be in a circumferentialdirection, which is substantially orthogonal to a line extending axiallybetween two pole faces of the same field pole member (not shown). Forexample, the directions of polarization 1241 can be substantiallyorthogonal to a line 1243 extending axially between two pole faces ofthe same field pole member. As shown, the surfaces of magnets 1232 a and1232 b can be polarized as south poles, whereby the flux entersmagnetically permeable material 1234 through surface 1235 in a mannerthat surface 1235 is a south pole (or is substantially a south pole) forrotor assembly 1230.

FIGS. 13A to 13C depict implementations of a magnet and magneticallypermeable material to form a magnetic region of a rotor magnet or rotorassembly, according to some embodiments. Diagram 1300 of FIG. 13Adepicts a magnetic region 1340 of a rotor assembly 1330, with magneticregion 1340 including magnets 1332 a and 1332 b and magneticallypermeable material 1334. In some embodiments, the magnetic material inrotor assembly 1330 has a portion (“W”) 1302 of an axial lengthdimension that is configurable to modify an amount of flux densitypassing through at least the surface of magnetically permeable structure1334.

FIG. 13B illustrates various views of a magnet 1332 a, according to anembodiment. View 1301 is a side view of magnet 1332 a showing a sidethat is polarized as a south pole (“S”). As shown, magnet 1332 a has aside portion 1351 b configured as a south pole in which flux enters.Further, magnet 1332 a also includes an axial extension area 1351 a thatcan be configured to increase an amount of flux passing through thesurface of magnetically permeable structure 1334. The amount of flux canbe varied by modifying either the width, W1, or the height, H1, or both,of axial extension area 1351 a. As such, an axial extension area can beconfigured to increase an amount of flux passing through the surface ofmagnetically permeable structure 1334. View 1311 depicts a front view ofsurface 1333 configured to confront a pole face, according to anembodiment. As shown, magnet 1332 a has a surface polarized in onedirection (e.g., as a north pole), and another surface polarized indirection indicative of a south pole. View 1321 is a side view of magnet1332 a showing a side that is polarized as a north pole (“N”). As shown,magnet 1332 a has a side portion 1353 b configured as a north pole inwhich flux emanates. Further, magnet 1332 a also includes an axialextension area 1353 a that can be configured to increase an amount offlux passing through the surface of magnetically permeable structure1334. The amount of flux can be varied by modifying either the width,W1, or the height, H1, or both, of axial extension area 1353 a or axialextension area 1351 a of view 1301, both of which may be the same area.Flux 1390 a can emanate normal to surface portion 1353 b as shown.

FIG. 13C illustrates various views of magnetically permeable material1334, according to an embodiment. View 1303 is a side view ofmagnetically permeable material 1334 showing a side of magneticallypermeable material 1334 that is configured to be disposed adjacent aside of magnet 1332 a to receive flux 1390 a from a north poleassociated with side portion 1353 b of FIG. 13B. In this view,magnetically permeable material 1334 includes a side portion 1361 bconfigured to be adjacent to side portion 1353 b of FIG. 13B and anaxial extension area 1361 a that is configured to be adjacent to axialextension area 1353 a. Axial extension area 1361 a includes a width, W2,or the height, H2, that can be modified (as can axial extension areas1351 a and 1353 a) to enhance the flux density passing through thesurface of magnetically permeable material 1334 to implement a magnetpole. Similarly, view 1321 is another side view of magneticallypermeable material 1334 showing another side that also is configured tobe disposed adjacent another side portion of a magnet not shown toreceive flux 1390 b from another north pole (e.g., from magnet 1332 b).In this side view 1321, magnetically permeable material 1334 includes aside portion 1363 b configured to be adjacent to another side portionand another axial extension area of another magnet not shown. View 1313depicts a front view of surface 1335 configured to confront a pole face,according to an embodiment. As shown, magnetically permeable material1334 has a surface 1335 configured to operate as a pole, such as a northpole, to provide flux 1392, the flux originating from magnets adjacentto the sides shown in views 1303 and 1321. In some embodiments, thesurface of magnetically permeable structure 1334 is configured toinclude a greater density of flux than a surface of magnet 1332 a ormagnet 1332 b. In various embodiments, the areas of the sides of magnet1332 a and magnet 1332 b are collectively greater than the surface areaof surface 1335.

FIGS. 13D to 13E depict examples of various directions of polarizationand orientations of surfaces of magnets and magnetically permeablematerial that form a magnetic region of a rotor magnet or rotorassembly, according to some embodiments. Diagram 1340 of FIG. 13Ddepicts a front view of magnets 1342 a and 1342 b, and magneticallypermeable material 1352 arranged radially about a centerline 1349. In atleast some embodiments the directions of polarization are normal to thesurfaces of either magnet surfaces or the surfaces of the magneticallypermeable material, or both. In some embodiments, rays 1344 a and 1344 bcan represent the directions of polarization for magnets 1342 a and 1342b. For example, a direction of polarization can be represented by ray1344 b extending from a point 1345 (in space or relative to magnetsurface), which can lie on a circle centered on a centerline (e.g., theaxis of rotation). A portion 1388 of the centered circle is shown indashed lines. The direction of polarization can be oriented tangent tothe circle in a plane centered on the centerline to produce flux in acircumferential direction. Thus, rays 1344 a and 1344 b can representthe directions of polarization for magnets 1342 a and 1342 b relative tothe magnet surfaces 1346 a and 1346 b. Directions of polarization formagnets 1342 a and 1342 b give rise to flux path portions representingflux passing circumferentially (i.e., the flux passes along a pathcircumscribed by a circle portion 1388 at a radial distance 1391 fromcenterline 1349). Thus, magnets 1342 a and 1342 b can be configured togenerate magnet flux along a circumferential flux path portion.According to some embodiments, magnets 1342 a and 1342 b are magnetizedsuch that the directions of polarization for magnets 1342 a and 1342 bare normal to the surfaces 1346 a and 1346 b, the normal vectorsdepicting the orientation of the surfaces 1346 a and 1346 b asrepresented by rays 1344 a and 1344 b. But magnets 1342 a and 1342 b canbe magnetized such that the directions of polarization for magnets 1342a and 1342 b can be at an angle to the surfaces 1346 a and 1346 b (i.e.,at an angle to a normal or a normal vector representing the direction ofthe surfaces of the magnets). According to some embodiments, a directionof polarization for a magnetic material, such as that in magnet 1342 b,can lie in a first plane 1393 perpendicular or substantiallyperpendicular to a second plane (e.g., plane 1387) including centerline1349 and a normal vector 1389 emanating from a point on confrontingsurface 1386 of magnetically permeable material 1352, whereby secondplane 1387 radially bisects magnetically permeable material 1352.Confronting surface 1386 is configured to confront a pole face of afield pole member.

In some embodiments, portions of the flux paths can be directedsubstantially between a first point of entry into (or exit from) amagnet and a second point of exit from (or entry to) the magnet. Thus,the portions of flux paths may be relatively straight (but need not be)within the magnetic material. For example, flux can pass substantiallystraight through a magnetic material such that it exits (or enters) themagnetic material corresponding to a direction of polarization. In someembodiments, portions of the flux path can originate from either surface1346 a or 1346 b. Flux can pass into magnetically permeable material1352, with its direction being altered such that it exits a surface ofmagnetically permeable material 1352 along, for example, a non-straightor curved flux path portion. In some examples, the flux path or fluxpath portions in magnetically permeable material 1352 can includenon-straight portions between a surface of magnetically permeablematerial 1352 adjacent to a magnet and a surface of magneticallypermeable material 1352 adjacent a pole face.

In some embodiments, rays 1344 a and 1344 b can represent the directionsof flux paths (or flux path portions) between a magnet and amagnetically permeable material. For example, rays 1344 a and 1344 b canrepresent a portion of a flux path at or near the interface between themagnet and the magnetically permeable material. In some embodiments,rays 1344 a and 1344 b can be coextensive with flux paths (or flux pathportions) passing through an interface between a magnet and amagnetically permeable material. Note that the depiction of flux pathsas rays 1344 a and 1344 b in FIGS. 13D and 13E is not intended to belimiting. For example, flux paths (or portions thereof) represented byrays 1344 a and 1344 b can be at any angle in any direction between amagnet and a magnetically permeable material (other than 0 degrees fromor parallel to a plane including a centerline 1349 and the magnetsurface) and may include straight portions and/or curved portions. Whilemagnet surfaces 1346 a and 1346 b and surfaces 1348 a and 1348 b aredepicted as being coextensive with planes parallel to centerline 1349,these surfaces are not intended to be limiting. Surfaces 1346 a and 1346b and surfaces 1348 a and 1348 b can be coextensive with planes that areat non-zero angles to centerline 1349.

Diagram 1360 of FIG. 13E depicts a perspective view of magnets 1342 aand 1342 b and magnetically permeable material 1352 arranged radiallyabout a centerline 1362. Thus, rays 1364 a and 1364 b can represent thedirections of polarization for magnets 1342 a and 1342 b and/or generaldirections of flux paths relative to (e.g., at angles Y and Z) the rays1364 a and 1364 b, which represent either normal vectors to magnetsurfaces or a tangent to a circle centered on centerline 1349 andpassing through a point in space, such as point 1345 of FIG. 13D. AnglesY and Z can represent any angle ranging from 0 to 65 degrees from rays1364 a and 1364 b (i.e., 90 to 25 degrees from a magnet surface).According to some embodiments, the term “substantially perpendicular,”when used to describe, for example, a direction of polarization, canrefer to a range of angles from a line portion, such as a normal vector,that is 90 degrees to at least a portion of a magnet surface. Or therange of angles can be referenced from the flux path formed between thesurface of magnetically permeable material and a pole face. In oneexample, a range of angles can include any angle from 0 to 65 degreesrelative to a normal vector (i.e., 90 to 25 degrees from a magnetsurface portion). In some embodiments, surfaces 1346 a and 1346 b andsurfaces 1348 a and 1348 b of FIG. 13D can be coextensive with planesthat are at angles to centerline 1362 (or a plane including centerline1362). For example, FIG. 13E depicts that the sides or surfaces ofmagnetically permeable material 1352 can be configured as surfaces 1366,which are coextensive with planes (not shown) at angles to centerline1362. Surface 1366 can increase the surface area of the sides ofmagnetically permeable material 1352, and may enhance the amount of fluxpassing through the surface of magnetically permeable material 1352 thatis configured to confront pole faces. According to various embodiments,directions of polarization and/or flux path portions may or may not varyfrom the directions of surfaces 1346 a and 1346 b of magnets or magneticmaterial and/or or surfaces 1348 a and 1348 b of magnetically permeablematerial. Further, directions of surfaces 1346 a and 1346 b of magnetsor magnetic material and/or or surfaces 1348 a and 1348 b ofmagnetically permeable material may or may not be flat and/or may or maynot be oriented in planes that at an angle to a plane including the axisof rotation. According to some embodiments, the term “substantiallynormal,” when used to describe, for example, a direction of orientationfor a magnet surface, can refer to a range of angles from a line that is90 degrees to a tangent plane having at least a point on the magnetsurface. Examples of angles in the range of angles include any anglefrom 0 to 65 degrees relative to a normal vector.

FIG. 14 is an exploded view of a rotor-stator structure 1400 includingrotor assemblies in accordance with some embodiments. FIG. 14 depicts arotor assembly including at least two rotor assemblies 1430 a and 1430 bmounted on or affixed to a shaft 1402 such that each of rotor assemblies1430 a and 1430 b are disposed on an axis of rotation that can bedefined by, for example, shaft 1402. A stator assembly can includeactive field pole members 1410 a arranged about the axis. An activefield pole member 1410 a can include a coil 1412, a field pole member1413 having pole faces 1414, and a bobbin 1415. A subset of pole faces1414 of active field pole members 1410 a can be positioned to confrontthe arrangement of magnetic regions 1440 in rotor assemblies 1430 a and1430 b to establish air gaps. In some embodiments, magnetic regions 1440can represent one or more surface magnets. Rotor assemblies 1430 a and1430 b can respectively include support structure 1438 a and supportstructure 1438 b. Further, bearings 1403 can be disposed within an axiallength between the ends of rotor assemblies 1430 a and 1430 b ofrotor-stator structure 1400.

FIG. 15 is an exploded view of a rotor-stator structure 1500 includingrotor assemblies in accordance with some embodiments. FIG. 15 depicts arotor assembly including at least two rotor assemblies 1530 a and 1530 bmounted on or affixed to a shaft 1502 such that each of rotor assemblies1530 a and 1530 b are disposed on an axis of rotation that can bedefined by, for example, shaft 1502. A stator assembly can includeactive field pole members 1510 a arranged about the axis. An activefield pole member 1510 a can include a coil 1512, a field pole member1513 having pole faces 1514, and a bobbin 1515. A subset of pole faces1514 of active field pole members 1510 a can be positioned to confrontthe arrangement of magnetic regions including magnets 1532 andmagnetically permeable structures 1534 in rotor assemblies 1530 a and1530 b to establish air gaps. Further, bearings 1503 can be disposedwithin an axial length between the ends of rotor assemblies 1530 a and1530 b of rotor-stator structure 1500.

FIG. 16 is an exploded view of a rotor-stator structure 1600 includinginner rotor assemblies in accordance with some embodiments. FIG. 16depicts a rotor assembly including at least two inner rotor assemblies1630 a and 1630 b mounted on or affixed to a shaft 1602 such that eachof inner rotor assemblies 1630 a and 1630 b are disposed on an axis ofrotation that can be defined by, for example, shaft 1602. FIG. 16depicts boundaries 1603 of conically-shaped spaces in which magneticregions 1690 are disposed. Pole faces 1614 are disposed or arrangedoutside boundaries 1603 of conically-shaped spaces. Thus, magneticregions 1690 are coextensive with an interior surface of a cone, whereaspole faces 1614 are coextensive with an exterior surface of a cone). Astator assembly 1640 can include active field pole members 1610 a, 1610b, and 1610 c arranged about the axis. An active field pole member 1610a can include a coil 1612 and pole faces 1614 formed at the ends offield pole member 1611 a. A subset of pole faces 1614 of active fieldpole members 1610 can be positioned to confront the arrangement ofmagnetic regions 1690 that can either include surface magnets (e.g.,magnetic material, including permanent magnets) and/or can include acombination of magnetic material (e.g., including permanent magnets) andmagnetically permeable structures as internal permanent magnets (“IPMs”)in rotor assemblies 1630 a and 1630 b to establish air gaps. Rotorassemblies 1630 a and 1630 b can respectively include support structure1638 a and support structure 1638 b.

FIG. 17 is a cross-section view of a rotor-stator structure includingboth outer and inner rotor assemblies in accordance with someembodiments. A rotor assembly including at least two rotor assemblies1738 a and 1738 b mounted on or affixed to a shaft 1702 such that eachof inner rotor assemblies includes magnetic regions 1732 b that aredisposed on an axis of rotation that can be defined by, for example,shaft 1702. Further, rotor assemblies 1738 a and 1738 b can also includemagnetic regions 1732 a of outer rotor assemblies. A stator assembly caninclude active field pole members 1710 a and 1710 b arranged about theaxis, both of which include coils 1712. A subset of pole faces of activefield pole members 1710 can be positioned to confront the arrangement ofmagnetic regions 1732 a and 1732 b that can either include surfacemagnets or can include magnets and magnetically permeable structures asinternal permanent magnets in rotor assemblies 1738 a and 1738 b toestablish air gaps. Rotor assemblies 1738 a and 1738 b can respectivelyinclude support structures and bearings 1703.

FIGS. 18A to 18D depict various views of an example of a magneticallypermeable structure (and surfaces thereof) with various structures ofmagnetic material, according to some embodiments. FIG. 18A is a frontperspective view 1800 of an example of a magnetically permeablestructure 1834 configured for use in inner and outer rotor assemblies.Magnetically permeable structure 1834 includes one or more confrontingsurfaces and a number of non-confronting surfaces. A “confrontingsurface” of a magnetically permeable structure is, for example, asurface configured to confront or face an air gap, a pole face, a fieldpole member, a stator assembly, or the like, whereas a “non-confrontingsurface” of a magnetically permeable structure is, for example, asurface configured to confront or face structures other than a poleface, according to various embodiments. A “non-confronting surface” canbe configured to face or confront magnetic material. In the exampleshown, magnetically permeable structure 1834 includes a confrontingsurface 1802 and a number of non-confronting surfaces 1803 a, 1803 b,and 1804. Magnetic material can be disposed adjacent surfaces 1803 a and1803 b, whereby the magnetic material can be polarized in a directioninto (or out from) surfaces 1803 a and 1803 b. Therefore,non-confronting surfaces 1803 a and 1803 b can include or can be on aflux path portion of a flux path passing through field pole members (notshown), magnetically permeable structure 1834, and the magnetic materialadjacent to non-confronting surfaces 1803 a and 1803 b. Non-confrontingsurface 1804 can be referred to as a “radial non-confronting surface,”as its surface area is disposed generally at a radial distance. Notethat magnetically permeable structure 1834 can be configured to formmagnetic regions in either inner or outer rotor assemblies. For example,if magnetically permeable structure 1834 is implemented in an outerrotor assembly, then magnetically permeable structure 1834 rotates aboutan axis 1801 b, whereas if magnetically permeable structure 1834 isimplemented in an inner rotor assembly, then magnetically permeablestructure 1834 rotates about an axis 1801 a.

FIG. 18B is a rear perspective view 1810 of an example of magneticallypermeable structure 1834 including an axial non-confronting surface foreither inner or outer rotor assemblies, according to one embodiment. Asshown, magnetically permeable structure 1834 includes a non-confrontingsurface 1805 that can be referred to as an “axial non-confrontingsurface.” Note that if magnetically permeable structure 1834 isimplemented in an outer rotor assembly, then magnetically permeablestructure 1834 rotates along circle 1813 about an axis 1812 b, whereasif magnetically permeable structure 1834 is implemented in an innerrotor assembly, then magnetically permeable structure 1834 rotates oncircle 1811 about an axis 1812 a.

FIG. 18C is a front perspective view 1820 of an example of anarrangement of a magnetically permeable structure 1834 and magneticstructures, according to one embodiment. As shown, a subset of magneticstructures including magnetic material, such as magnetic structures 1832a and 1832 b, are disposed adjacent to non-confronting surfaces 1803 aand 1803 b, respectively. The flux produce by magnetic structures 1832 aand 1832 b (e.g., permanent magnets) is directed to magneticallypermeable structure 1834, which, in turn, can pass through confrontingsurface 1802 to a pole face (not shown). For purposes of illustration,consider that FIG. 8A depicts magnetically permeable structure 1834being implemented as magnetically permeable structure 834 a of rotorassembly 830 a, and magnetic structures 1832 a and 1832 b of FIG. 18Care implemented as 832 d and 832 b, respectively, of FIG. 8A. As shown,magnetic structures 832 b and 832 d lie in or on flux path portions 891b and 891 c, respectively, (or shorter portions of flux path portions891 b and 891 c). Flux path portions 891 b and 891 c extends betweenrotor assemblies 830 a and 830 b. The non-confronting surfaces ofmagnetically permeable structure 834 a adjacent magnetic structures 832b and 832 d also can be on or in the flux path portions 891 b and 891 c(or shorter portions thereof). Flux path portions 891 b and 891 c (and891 a) of FIG. 8A can be described as principal flux path portions asthe predominant amount of flux passes along these flux path portions,according to some embodiments. As is discussed below, other flux pathscan be implemented to intercept flux path portions 891 b and 891 c (and891 a) to, among other things, provide additional flux to thatassociated with the principal flux path portions.

Referring back to FIG. 18C, supplementary magnetic material is disposedadjacent to non-confronting surfaces of magnetically permeable structure1834 to enhance the flux of flux paths having portions passing throughmagnetic structures 1832 a and 1832 b and confronting surface 1802. Inthe example shown, a magnetic structure 1822 (e.g., a permanent magnet)is disposed adjacent non-confronting surface 1804, whereby the directionof polarization for magnetic structure 1822 is directed into (or out of)non-confronting surface 1804. As such, magnetic structure 1822 canprovide additional flux to enhance the flux passing through confrontingsurface 1802.

FIG. 18D is a rear perspective view 1830 of an example of thearrangement depicted in FIG. 18C, according to some embodiments.Additional supplementary magnetic material is disposed adjacent tonon-confronting surface 1805 of magnetically permeable structure 1834 toenhance the flux of flux paths having portions passing through magneticstructures 1832 a and 1832 b and confronting surface 1802. As shown, amagnetic structure 1833 (e.g., a permanent magnet) is disposed adjacentnon-confronting surface 1805, whereby the direction of polarization formagnetic structure 1833 is directed into (or out of) non-confrontingsurface 1805. As such, magnetic structure 1833 can provide additionalflux to enhance the flux passing through confronting surface 1802.

FIG. 18E is a front perspective view 1840 of an example of amagnetically permeable structure including an extension portion 1845,according to some embodiments. A magnetically permeable structure 1808includes an extension portion 1847 to vary an amount of flux passingthrough confronting surface 1802, whereby the amount of flux can bevaried by modifying a dimension of magnetically permeable structure 1808along the axis (i.e., in an axial direction). Extension portion 1847provides for additional surface area of non-confronting surfaces, andcan be composed of material similar to that of the magneticallypermeable material. For example, additional surface area 1855 isprovided so that supplementary magnetic material, such as magneticstructure 1844 a, can be disposed adjacent to additional surface area1855 (another magnetic structure 1844 b can also be disposed adjacent toadditional surface area not shown). The supplementary magnetic materialcan provide for enhanced amounts of flux being passed throughconfronting surfaces 1802. Therefore, the additional surface area andsupplementary magnetic material can be added optionally to enhance theflux produced by the magnetic region including confronting surface 1802.

Extension portion 1847 can also provide additional surface area 1856 sothat supplementary magnetic material, such as magnetic structure 1842,can be disposed adjacent to additional surface area 1856 to enhance theflux passing through confronting surface 1802. Further, extensionportion 1847 can also provide additional surface area 1845 so that yetother supplementary magnetic material, such as magnetic structure 1835,can be disposed adjacent to additional surface area 1845 to enhance theflux. In some embodiments, magnetic structures 1842 and 1835 can bereferred to as radial boost magnets, whereas magnetic structure 1833 canbe referred to as an axial boost magnet. A radial boost magnet canproduce flux parallel to or along a radial direction relative to anaxis, according to some embodiments. For example, a radial boost magnetcan produce flux perpendicular to (or substantial perpendicular to) anaxis of rotation. An axial boost magnet can produce flux parallel to oralong an axial direction, according to some embodiments. For example, anaxial boost magnet can produce flux parallel to (or substantial parallelto) an axis of rotation. In various embodiments, one or more of magneticstructures 1833, 1835, 1842, 1844 a, and 1844 b can be optional. More orfewer surfaces and/or magnetic structures can be implemented. Forexample, any of magnetic structures 1842, 1844 a, and 1844 b can beformed as part of respective magnetic structures 1822, 1832 a, and 1832b to form unitary magnetic structures (e.g., magnetic structures 1822and 1842 can be formed as a single magnet). Note that magneticstructures and a magnetically permeable structure depicted in FIGS. 18Ato 18E are not limited to those shapes shown and are not limited to flatsurfaces. Note that boost magnets can be made from the same magnetmaterial or different magnet material that is disposed betweenmagnetically permeable material in the rotor assemblies. Further, boostmagnets can have the same or different surface area dimensions as theadjacent surfaces of magnetic permeable material.

FIGS. 18F and 18G are side views of an example of magnetically permeablestructure and various axes of rotations, according to some embodiments.FIG. 18F is a side view of a magnetically permeable structure 1808oriented relative to an axis of rotation 1852. As confronting surface1802 is oriented to face away from axis of rotation 1852, magneticallypermeable structure 1808 is implemented in an inner rotor assembly. Inan inner rotor assembly, a radial surface 1862 (i.e., a radialnon-confronting surface) is disposed at an inner radius (“IR”)dimension, whereas a radial surface 1864 is disposed at an outer radius(“OR”) dimension. Non-confronting surface 1866 is an axialnon-confronting surface. FIG. 18G is a side view of a magneticallypermeable structure 1808 oriented relative to an axis of rotation 1854.As confronting surface 1802 is oriented to face toward axis of rotation1854, magnetically permeable structure 1808 is implemented in an outerrotor assembly. In an outer rotor assembly, a radial surface 1865 (i.e.,a radial non-confronting surface) is disposed at an inner radius (“IR”)dimension, whereas a radial surface 1863 is disposed at an outer radius(“OR”) dimension. Non-confronting surface 1866 is an axialnon-confronting surface. Radial surfaces 1862, 1863, 1864, and 1865 areoriented to extend generally along the axis of rotation, whereas axialsurface 1866 is oriented to extend generally along one or more radii.

FIGS. 19A to 19D depict various views of an example of an outer rotorassembly, according to some embodiments. FIG. 19A is a front view of anouter rotor assembly 1900. Outer rotor assembly 1900 includes magneticmaterial 1982 a and 1982 b (or structures thereof, such as magnets) andmagnetically permeable material 1984 arranged about a centerline 1989,the combination of which form magnetic regions, such as magnetic region1940. Outer rotor assembly 1900 also includes boost magnets disposedadjacent to one or more non-confronting surfaces of magneticallypermeable material 1984. As used herein, the term “boost magnet” canrefer, at least in some embodiments, to magnets disposed at or adjacenta surface of magnetically permeable material to enhance or “boost” theflux exchanged between a confronting surface of the magneticallypermeable material and a pole face of a field pole member. A boostmagnet can be disposed external to the flux paths (or flux pathportions) passing through magnetically permeable material 1984 andmagnetic material 1982 a and 1982 b (e.g., external to the principalflux paths). The boost magnet produces flux for enhancing the amount offlux passing through the air gaps, which, in turn, enhances torqueproduction. As shown, outer rotor assembly 1900 includes boost magnetsdisposed radially (e.g., at a radial distance from centerline 1989),such as at an inner radius or an outer radius. In some examples,magnetic material can be disposed at an outer radial dimension (“OR”)1988 b as one or more outer radial boost magnets. As shown, outer rotorassembly 1900 includes boost magnets 1972 a and 1972 b. While boostmagnets 1972 a and 1972 b are depicted as having square or rectangularcross-sections, boost magnets are not so limited and can be formed withone or more magnets having various cross-sectional shapes. In anotherexample, a boost magnet can be disposed at an inner radial dimension(“IR”) 1988 a. A magnetic material can be disposed at inner radialdimension 1988 a as one or more inner radial boost magnets. In FIG. 19A,the boost magnet at the inner radial dimension 1988 a is composed ofinner radial boost magnet 1974 disposed adjacent a surface ofmagnetically permeable material 1984 located at inner radial dimension1988 a. In some examples, inner radial boost magnet 1974 can be amonolithic structure with alternating regions of “north” and “south”polarities, or can be composed of separate magnetic structuresintegrated to form inner radial boost magnet 1974.

FIG. 19B is a front perspective view of an outer rotor assembly 1950implementing outer radial boost magnets 1972 a and 1972 b, as well asinner radial boost magnet(s) 1974, according to some embodiments.Further, one or more boost magnet(s) can be located at or adjacent othersurfaces of magnetically permeable material 1984, such as the rearsurface(s) of magnetically permeable material 1984. As shown, a boostmagnet structure 1976 a is disposed adjacent the rear surfaces ofmagnetically permeable material 1984. Boost magnet structure 1976 a isconfigured to modify (e.g., increase) the amount of flux passing throughmagnetic region 1940 of FIG. 19A. Note that any outer radial boostmagnets 1972 a and 1972 b, inner radial boost magnet 1974, and axialboost magnet structure 1976 a can be optional and may be omitted. Note,too, that the one or more of the boost magnets of FIGS. 19A and 19B caninclude magnetic material and other material to produce flux.

FIG. 19C is a rear view of an outer rotor assembly 1960 illustratingboost magnets 1972 a and 1972 b, boost magnet(s) 1974, and variousexamples of boost magnet structures 1976 a, according to someembodiments. In various embodiments, boost magnet structure(s) 1976 acan be composed of one or more entities configured to provide magneticmaterial having varied directions of polarization. In some examples,boost magnet structure(s) 1976 a can be a monolithic structure includingdifferent regions of polarity, such as region 1976 b, to provide flux ina direction generally along centerline 1989. As shown, two boost magnetstructure(s) 1976 a can be used, whereby boost magnet structure 1976 arepresents one-half of the rear view of an outer rotor assembly 1960(the other one-half is not shown). In some examples, a boost magnetstructure 1976 a can be composed of separates structures 1977, each ofwhich includes different regions of polarity to provide the flux alongcenterline 1989. As shown, four boost magnets 1977 (including 1977 a)can be implemented in lieu of a boost magnet structure such as boostmagnet structure 1976 a. The four boost magnets 1977 represent one-halfof the rear view of outer rotor assembly 1960 (the other four boostmagnets 1977 representing the other half are not shown). Further, theboost magnet 1977 a is depicted as having a direction of polarization,in the rear view, as a south (“S”) magnet pole. The direction ofpolarization of boost magnet 1977 a is such that a north (“N”) magnetpole (see FIG. 19D) extends from the other side (i.e., the front side)of boost magnet 1977 a. FIG. 19C also depicts a direction ofpolarization of inner radial boost magnet 1974 (i.e., from south (“S”)to north (“N”), directed inwardly toward centerline 1989. FIG. 19C alsodepicts directions of polarization of outer radial boost magnets 1972 cand 1972 d. Magnets 1982 a and 1982 b include magnetic material havingdirections of polarization that are generally tangential (orsubstantially tangential) to a circle (not shown) about centerline 1989.Directions of polarization of outer radial boost magnets 1972 a and 1972b are shown as being from south (“S”) to north (“N”), directed outwardlyaway from centerline 1989. In view of, for example, the polarizationdirections of magnets 1982 a and 1982 b, and of other magnets, a spacebehind the surface of boost magnet 1977 a is configured to provide anorth magnet pole and a space behind the surface of region 1976 b isconfigured to provide a south magnet pole.

FIG. 19D a front, perspective view of an example of an outer rotorassembly 1990 illustrating directions of polarization to form and/orenhance a magnetic region, according to some embodiments. FIG. 19Ddepicts the directions of polarization for forming flux paths (or fluxpath portions) as well as other flux paths (or other flux path portions)configured to enhance the flux associated with the flux paths. Forexample, magnets 1982 a and 1982 b include directions of polarizationsuch that magnets 1982 a and 1982 b magnetically cooperate to form anorth (“N”) magnet pole. As such, confronting surface 1985 ofmagnetically permeable material 1984 forms a magnetic region (or aportion thereof) as a north magnet pole. Outer radial boost magnets 1972c and 1972 d can generate flux directed along a north (“N”) direction ofpolarization into magnetically permeable material 1984 at or approximateto an outer radial dimension. Inner radial boost magnet 1974 cangenerate flux directed along a north (“N”) direction of polarizationinto magnetically permeable material 1984. Axial boost magnet 1977 a cangenerate flux directed along a north (“N”) direction of polarizationinto magnetically permeable material 1984 at or approximate to an innerradial dimension. Therefore, magnetic material associated with outerradial boost magnets 1972 c and 1972 d, inner radial boost magnet 1974,and axial boost magnet 1977 a can produce flux to enhance the fluxpassing on flux paths or flux path portions in a manner that flux perunit surface area of confronting surface 1985 is enhanced.

FIG. 20 depicts an exploded, front perspective view of a portion of anouter rotor assembly, according to some embodiments. Outer rotorassembly 2000 is shown to include flux paths or flux path portionscontributing to the flux passing through magnetic regions that include,for example, magnets 1982 a and 1982 b and magnetically permeablematerial 1984 arranged about a centerline 2089. Magnets 1982 a and 1982b are shown to generate flux path portions 2021 and 2023, respectively,to magnetically couple with non-confronting surfaces of magneticallypermeable material 1984 that are on a flux path (e.g., a principal fluxpath) passing through the air gaps (not shown). Magnets 1982 a and 1982b include surfaces that are disposed adjacent portions 2031 and 2033,respectively, of axial boost magnet structure 1976 a when assembled.Outer boost magnets 1972 a and 1972 b can generate flux path portions2011 and 2013 to magnetically couple with surfaces 2072 a and 2072 b,respectively, of magnetically permeable material 1984. Inner boostmagnet 1974 is configured to generate flux path portion 2025 tomagnetically couple with a surface of magnetically permeable material1984. Further, axial boost magnet structure 1976 a includes a surfacearea 2032 of magnetic material having a direction of polarizationconfigured to generate a flux path portion 2015 to magnetically couplewith a rear non-confronting surface of magnetically permeable material1984. In various embodiments, flux path portions 2011, 2013, 2015, and2025 intersect, but lie external to (or off of), flux paths or flux pathportions that pass through magnets 1982 a and 1982 b. The fluxassociated with flux path portions 2011, 2013, 2015, and 2025 isprovided to enhance the flux passing through confronting surfaces 1985.

Note that flux in magnetically permeable material 1984 from the one ormore boost magnets can be additive through superposition. In someembodiments, the boost magnets are configured to reduce flux leakage.Outer radial boost magnets 1972 a and 1972 b can generate magnetic fieldpotentials vectorially directed as shown by rays 2011 and 2013 in FIG.20 to magnetically couple with surfaces 2072 a and 2072 b, respectively,of magnetically permeable material 1984. Inner radial boost magnet(s)1974 can be configured to generate magnetic field potential vectoriallydirected as shown by ray 2025 to magnetically couple with a surface ofmagnetically permeable material 1984. Further, axial boost magnetstructure 1976 a includes a surface area 2032 of magnetic material thatcan generate magnetic field potential vectorially directed as shown byray 2015 to magnetically couple with a rear non-confronting surface ofmagnetically permeable material 1984. In various embodiments, themagnetic field potentials illustrated by rays 2011, 2013, 2015 and 2025can facilitate the restriction of flux path portions 2021 and 2023 inmagnetically permeable material 1984 to the principal flux path passingthrough the air gaps. Such magnetic field potentials are disposedoutside the principal flux paths but do enhance the flux passing throughconfronting surfaces 1985. In view of the foregoing, the boost magnetscan operate to enhance flux by providing optimal magnetic return pathsthan otherwise might be the case. For example, boost magnets can providea magnetic return path that has a lower reluctance than otherwise mightbe the case (e.g., through air, a motor case, or any other externalentity). A reduction in reluctance improves the amount of availableflux.

FIG. 21 depicts a portion of an exploded, front perspective view ofanother outer rotor assembly, according to some embodiments. Outer rotorassembly 2100 is shown to include another implementation of a radialboost magnet. As shown, radial boost magnet 2102 includes one or moresurfaces that are curved, such as, a curved surface polarized as a south(“S”) magnet pole and another curved surface polarized as a north (“N”)magnet pole. One or more of these surfaces can be coextensive with anarc or a circle (not shown) centered on centerline 2089. Magneticallypermeable material 1984 is disposed between magnets 1982 a and 1982 b,and radially from inner boost magnet structure 1974. In this example, anon-confronting surface 2104 of magnetically permeable material 1984 isconfigured to be coextensive with a surface of radial boost magnet 2102.

FIGS. 22A to 22D depict various views of another example of an outerrotor assembly, according to some embodiments. FIG. 22A is a front viewof an outer rotor assembly 2200. Outer rotor assembly 2200 includesmagnetic material 2282 a and 2282 b (or structures thereof, such asmagnets) and magnetically permeable material 2284 arranged about acenterline 2289, the combination of which form magnetic regions, such asmagnetic region 2240. Outer rotor assembly 2200 also includes boostmagnets disposed adjacent to radial surfaces of magnetically permeablematerial 2284. As shown, outer rotor assembly 2200 includes boostmagnets disposed radially at an outer radius (i.e., at or adjacent anouter radial dimension (“OR”) 2288 b) as outer radial boost magnets2074. In this example, an outer radial boost magnet 2074 is a“breadloaf”-shaped magnetic structure (i.e., a breadloaf magnet).Breadloaf magnet 2074 includes a first surface that is flat (orrelatively flat) and a second surface that is curved (or relativelycurved), whereby the second surface is located at a greater radialdistance from centerline 2289 than the first surface. In variousexamples, the second surface is coextensive with an arc or a circle (notshown) at a specific radial distance from centerline 2289, such as outerradial dimension (“OR”) 2288 b. Breadloaf magnet 2074 provides for fewersingular structures that may constitute a boost magnet (e.g., breadloafmagnet 2074 can replace two or more boost magnets having rectangularcross sections), thereby simplify manufacturing of outer rotor assembly2200, among other things. Also, breadloaf magnet 2074 provides foradditional magnetic material 2201 over a boost magnet having arectangular cross-section, thereby providing for an increased capacityfor producing more flux, among other things. Further to FIG. 22A, aboost magnet structure can be disposed at or adjacent an inner radialdimension (“IR”) 2288 a as an inner radial boost magnet 2274.

FIG. 22B is a front perspective view of an outer rotor assembly 2250illustrating outer radial boost magnets and corresponding magneticallypermeable structures, according to some embodiments. Outer rotorassembly 2250 includes magnetically permeable material, such asmagnetically permeable structures 2284, and magnetic material, such asmagnets 2282 a and 2282 b. Further, outer rotor assembly 2250 includesboost magnets, which can include one or more of outer radial boostmagnets 2074, one or more inner boost magnets 2274, and/or one or moreaxial boost magnets, as represented by axial boost magnet structure 2276a. In the example shown, magnetically permeable structure 2284 includesa non-confronting surface 2262 shaped to coincide with a surface ofbreadloaf magnet 2074. For example, non-confronting surface 2262 is aradial non-confronting surface that is flat (or relatively flat) and canbe oriented orthogonal to a ray (not shown) extending from centerline2275.

FIG. 22C is a rear view of an outer rotor assembly of FIG. 22B,according to some embodiments. In this figure, axial boost magnetstructure 2276 a is absent and outer rotor assembly 2260 includes boostmagnets 2074 and an example of suitable magnetically permeablestructures 2284. Magnetically permeable structures 2284 each include anaxial non-confronting surface 2205.

FIG. 22D is a perspective side view of an outer rotor assembly of FIG.22C, according to some embodiments. In this figure, outer rotor assembly2290 includes magnetically permeable material disposed between magnets2282 a and 2282 b, which have directions of polarization arranged toconfigure the magnetically permeable material between magnets 2282 a and2282 b as a north (“N”) magnet pole. Note, too, that the magneticallypermeable structures of FIG. 22D have axial non-confronting surfaces2205. Further, outer boost magnets 2074 and inner boost magnets 2274 areincluded to boost flux in the magnetically permeable material. Axialboost magnet structure 2276 a includes different regions of polarity,such as region 2276 b, to provide flux in directions generally along thecenterline. Region 2276 b has a direction of polarization (e.g., a northpole) oriented to enter axial non-confronting surface 2205.Alternatively, axial boost magnet structure 2276 a can be replaced with,or can include, discrete magnets, such as axial boost magnet 2277, thatcan be disposed adjacent axial non-confronting surfaces 2205. Axialboost magnet 2277 is representative of other axial boost magnets, too,but those other axial boost magnets not shown.

FIG. 23A is a front view of an outer rotor assembly 2300 includingexamples of flux conductor shields, according to some embodiments. Outerrotor assembly 2300 includes magnetic material 2282 a and 2282 b (orstructures thereof, such as magnets) and magnetically permeable material2284. Outer rotor assembly 2300 also can include outer radial boostmagnets 2074 a and 2074 b, as well as an inner radial boost magnetstructure 2274. Further, FIG. 23A depicts flux conductor shieldsconfigured to provide a return flux path (or a portion thereof) for oneor more magnets, the return flux path portion residing in or traversingthrough a flux conductor shield. In some embodiments, a return flux pathportion lies externally to a flux path or flux path portion that passesthrough magnetic material, such as magnetic material 2282 a and 2282 b,disposed between magnetically permeable material 2284. A flux conductorshield reduces or eliminates flux (e.g., stray flux) associated withmagnets, such as boost magnets, that otherwise might extend externallyfrom outer rotor assembly 2300 or its components. Therefore, the fluxconductor shield can minimize or capture flux that otherwise might passthrough external materials that might cause losses, such as eddy currentlosses or hysteresis losses. As such, a flux conductor shield canminimize or negate magnetic-related losses due to structures locatedexternal to outer rotor assembly 2300. In some examples, a fluxconductor shield can operate to enhance flux by providing optimalmagnetic return paths for boost magnets than otherwise might be thecase. For example, a flux conductor shield can provide a magnetic returnpath that has a lower reluctance than otherwise might be the case (e.g.,through air, a motor case, or any other external entity). A reduction inreluctance improves the amount of available flux (e.g., as generated bythe boost magnets).

In the example shown, a flux conductor shield 2302 is configured tominimize or eliminate flux extending into an external region 2301 thatmight include magnetically permeable material, such as a motor housing.Thus, flux conductor shield 2302 includes a return flux path portion2311 extending from outer radial boost magnet 2074 a to outer radialboost magnet 2074 b, both of which have directions of polarization asdepicted in FIG. 23A. Another flux conductor shield 2304 is configuredto minimize or negate flux that otherwise might extend into an externalregion 2303 (i.e., a space defined by an inner radial dimension), whichmight include magnetically permeable material (e.g., a shaft). Thus,flux conductor shield 2304 includes a return flux path portion 2313extending from a portion 2386 of inner radial boost magnet structure2274 to another portion 2388 of inner radial boost magnet structure2274, with portions 2386 and 2388 having directions of polarization asdepicted in FIG. 23A.

According to some embodiments, a flux conductor shield can be composedof one or more constituent structures, which can include one or morestructures of magnetically permeable material or other materials. A fluxconductor shield can be formed from a strip of magnetically permeablematerial that is wound about itself a number of times to form, forexample, flux conductor shield 2302 or flux conductor shield 2304,according to some embodiments. For example, flux conductor shield 2302and flux conductor shield 2304 can be formed from, for example,grain-oriented material (e.g., from a grain-oriented steel lamination),with the grain being oriented circumferentially or along acircumference. Thus, the grain can be oriented to facilitate fluxpassage (e.g., reduce losses) along the predominant parts of return fluxpath portions 2311 and 2313. In specific embodiments, a flux conductorshield can be composed with multiple structures, such as concentriccircular structures of magnetically permeable material. But note that aflux conductor shield can include non-magnetically permeable material,such as plastic, to increase a distance between a boost magnet andmagnetically permeable material in either region 2301 or 2303, accordingto some embodiments. Such a plastic structure is configured as a spacerto increase the distance, thereby decreasing the strength of the flux atmagnetically permeable structures in either regions 2301 or 2303.Decreasing the strength of the flux can reduce magnetic losses.

FIG. 23B is an exploded, front perspective view of an outer rotorassembly including examples of flux conductor shields, according to someembodiments. In diagram 2300, an outer rotor assembly 2306 includes aninner radial flux conductor shield 2304 disposed within inner radialboost magnets that are positioned at an inner radial dimension fromcenterline 2275. The outer rotor assembly 2306 also includes an outerradial flux conductor shield 2302 disposed externally from the outerradial boost magnets. A motor housing portion 2308 is configured tohouse outer rotor assembly 2306, whereby outer radial flux conductorshield 2302 is configured to reduce flux from passing between outerrotor assembly 2306 and motor housing portion 2308.

FIG. 23C is an exploded, rear perspective view of an outer rotorassembly including examples of flux conductor shields and return fluxpath portions, according to some embodiments. Outer rotor assembly 2360includes an inner radial flux conductor shield 2304 disposed within aninner radial boost magnet structure 2274 that includes regions 2374 aand 2374 b of magnetic material, whereby the directions of polarizationof regions 2374 a and 2374 b of magnetic material establish a returnflux path portion 2395 within inner radial flux conductor shield 2304.Outer rotor assembly 2360 also includes an outer radial flux conductorshield 2302 disposed externally to an arrangement 2362 of outer radialboost magnets 2074, including outer radial boost magnets 2074 a and 2074b. The directions of polarization of outer radial boost magnets 2074 aand 2074 b establish a return flux path portion 2394 within outer radialflux conductor shield 2302. Further, outer rotor assembly 2360 alsoincludes an axial flux conductor shield 2368 disposed adjacent to anaxial boost magnet structure 2276 a having different regions ofpolarity, such as regions 2391 and 2393. The directions of polarizationof regions 2392 and 2393 establish a return flux path portion 2392within one or more portions of axial flux conductor shield 2368, such asin axial shield 2366 a. Note that while FIG. 23C depicts axial fluxconductor shield 2368 as composed of a number of disc-like structures,axial flux conductor shield 2368 need not be so limited. In one example,axial flux conductor shield 2368 can be formed from a corkscrew-shapedpiece of magnetically permeable material. In other examples, axial fluxconductor shield 2368 can be composed of multiple pieces for each axialshield constitute component 2366. Therefore, for example, axial shieldcomponent 2366 a can include multiple pieces, each being an arc-likeshape (not shown) configured to provide a return flux path portionbetween regions 2391 and 2393. A piece can be implemented withgrain-oriented material with the grain being oriented generally from oneof regions 2391 and 2393 to the other. According to some embodiments, areturn flux path can originate at a boost magnet of a first rotorassembly and traverse through magnetically permeable material into afield pole member. The return flux path then can exit the field polemember and pass through another magnetically permeable structure of asecond rotor assembly. The return flux path then passes through anotherboost magnet, through a flux conductor shield, and into yet anotherboost magnet. Then the return flux path continues in a similar manneruntil reaching the point of origination at the boost magnet of the firstrotor assembly. Consequently, the return flux path need not pass throughmagnetic material disposed between the magnetically permeable structuresof a rotor assembly. In some embodiments, return flux path portions2392, 2394 and 2395 lie off the principal flux paths, such as those fluxpaths passing circumferentially from one structure of magneticallypermeable material through magnetic material and into another structureof magnetically permeable material.

FIGS. 24A to 24C depict various views of an example of an inner rotorassembly, according to some embodiments. FIG. 24A is a front perspectiveview of an inner rotor assembly 2400 in accordance with a specificembodiment. Inner rotor assembly 2400 includes magnetic material 2482 aand 2482 b (or structures thereof, such as magnets) and magneticallypermeable material 2484 arranged about a centerline, all of which formmagnetic regions, such as magnetic region 2440. Further, magneticallypermeable material 2484 includes a confronting surface 2485 configuredto confront a pole face of a field pole member (not shown), confrontingsurface 2485 being oriented at an angle to a centerline or axis ofrotation. An arrangement 2401 of magnet 2482 a, magnetically permeablematerial 2484, and magnet 2482 b is shown in an exploded view, withmagnets 2482 a and 2482 b being oriented so that the north (“N”)directions of polarization are directed into magnetically permeablematerial 2484. Note that magnets 2482 a and 2482 b can include an axialextension area 2451, which can provide, among other things, an enhancedsurface area through which a greater amount of flux can pass. Innerrotor assembly 2400 optionally can include an end cap 2402 that can,among other things, provide support (e.g., compressive support) toimmobilize magnetic material 2482 a and 2482 b, and magneticallypermeable material 2484 against rotational forces as inner rotorassembly 2400 rotates at relatively high revolutions per unit time aboutan axis of rotation. End cap 2402, therefore, can be implemented tomaintain air gap dimensions during various rotational speeds.

FIG. 24B is a side view of an inner rotor assembly 2420 in accordancewith a specific embodiment. An outer radius dimension can vary in anangled surface portion (e.g., in an angled surface portion 2428) alongthe axis of rotation, and the outer radius dimension can be relativelyconstant in an extension portion (e.g., in an extension region 2426).Also shown is a radial non-confronting surface 2490 of magneticallypermeable material 2484, adjacent which an outer radial boost magnet canbe disposed. FIG. 24C is an exploded front view of structures of amagnetic region in an inner rotor assembly in accordance with a specificembodiment. A portion 2460 of an inner rotor assembly 2490 is shown toinclude magnet 2482 a, magnetically permeable material 2484, and magnet2482 b, as well as an outer radial boost magnet 2476 and an axial boostmagnet 2477. Outer radial boost magnet 2476 is disposed adjacent radialnon-confronting surface 2490, and axial boost magnet 2477 is disposedadjacent an axial on-confronting surface (not shown). As shown, surfacesof magnet 2482 a, magnet 2482 b, outer radial boost magnet 2476, andaxial boost magnet 2477 having a north (“N”) direction of polarizationare oriented toward non-confronting surfaces of magnetically permeablematerial 2484. Therefore, confronting surface 2485 is configured as amagnet pole polarized as a “north” pole.

FIGS. 25A to 25B depict exploded views of an example of an inner rotorassembly, according to some embodiments. FIG. 25A is a front perspectiveview of an inner rotor assembly 2500 in accordance with a specificembodiment. Inner rotor assembly 2500 includes an inner rotor assemblyas an arrangement 2502 of magnetic material (or structures thereof, suchas magnets) and magnetically permeable material. Also shown are outerradial boost magnets 2476 disposed on and/or adjacent radialnon-confronting surfaces (e.g., in the extension portion) of themagnetically permeable material. Axial boost magnets 2477 can includemagnetic material having surfaces oriented toward the rear (or axial)non-confronting surfaces of the magnetically permeable material withalternating directions of polarization. An outer radial flux conductorshield 2510 is disposed over outer radial boost magnets 2476, and anaxial flux conductor shield 2514 including one or more axial shieldstructures 2512 are disposed on and/or adjacent the axial boost magnets2477. FIG. 25B is a rear perspective view of inner rotor assembly 2500of FIG. 25A. As shown, axial boost magnets 2477 are disposed adjacentrear (or axial) non-confronting surfaces 2405 of the magneticallypermeable material of inner rotor assembly 2550.

FIG. 26 is an exploded view of a rotor-stator structure including innerrotor assemblies in accordance with some embodiments. Rotor-statorstructure 2600 includes a stator assembly 2610 and inner rotorassemblies 2602 a and 2602 b. Stator assembly 2610 can include a numberof field pole members 2622 having coils 2620 formed thereon, and anumber of pole faces 2614 configured to confront the surfaces of innerrotor assemblies 2602 a and 2602 b. Inner rotor assemblies 2602 a and2602 b can also include one or more of outer radial boost magnets 2476and axial boost magnets 2477. In some examples, inner rotor assemblies2602 a and 2602 b can include inner radial boost magnets (not shown). Inother embodiments, inner rotor assemblies 2602 a and 2602 b can bereplaced by rotor assemblies having cylindrical confronting surfaces, aswell as outer radial boost magnets and axial boost magnets configured toenhance flux in flux paths formed through cylindrically-shaped rotorassemblies. Note that pole faces 2614 can include concave pole facesthat are configured to confront convex-shaped portions of magneticregions of inner rotor assemblies 2602 a and 2602 b. An example of aconvex-shaped portion of a magnetic region if magnetic region 2440 ofFIGS. 24A and 24B.

Various embodiments or examples of the invention may be implemented innumerous ways, including as a system, a process, an apparatus, or aseries of program instructions on a computer readable medium such as acomputer readable storage medium or a computer network where the programinstructions are sent over optical, electronic, or wirelesscommunication links. In general, operations of disclosed processes maybe performed in an arbitrary order, unless otherwise provided in theclaims.

A detailed description of one or more examples has been provided abovealong with accompanying figures. The detailed description is provided inconnection with such examples, but is not limited to any particularexample. The scope is limited only by the claims, and numerousalternatives, modifications, and equivalents are encompassed. Numerousspecific details are set forth in the following description in order toprovide a thorough understanding. These details are provided as examplesand the described techniques may be practiced according to the claimswithout some or all of the accompanying details. For clarity, technicalmaterial that is known in the technical fields related to the exampleshas not been described in detail to avoid unnecessarily obscuring thedescription.

The description, for purposes of explanation, uses specific nomenclatureto provide a thorough understanding of the various embodiments. However,it will be apparent that specific details are not required in order topractice the various embodiments. In fact, this description should notbe read to limit any feature or aspect of to any embodiment; ratherfeatures and aspects of one example can readily be interchanged withother examples. Notably, not every benefit described herein need berealized by each example of the various embodiments; rather any specificexample may provide one or more of the advantages discussed above. Inthe claims, elements and/or operations do not imply any particular orderof operation, unless explicitly stated in the claims. It is intendedthat the following claims and their equivalents define the scope of thevarious embodiments.

The invention claimed is:
 1. A rotor-stator structure for anelectrodynamic machine comprising: a stator assembly comprising: fieldpole members arranged about an axis of rotation and including pole facesat the ends of the field pole members, a subset of the pole facesincluding pole face portions coextensive with a boundary of aconically-shaped space; and one or more rotor assemblies arranged on theaxis of rotation, each of the one or more rotor assemblies comprising:magnetically permeable structures positioned radially about the axis ofrotation, the magnetically permeable structures comprising: confrontingsurfaces oriented at an angle to the axis of rotation to form air gapswith at least the pole face portions, and non-confronting surfaces; oneor more groups of magnetic structures including magnetic material, theone or more groups of the magnetic structures comprising: a first groupof the magnetic structures interleaved with the magnetically permeablestructures; a second group of the magnetic structures; and a fluxconductor shield disposed adjacent to the second group of the magneticstructures, the flux conductor shield configured to provide return fluxpaths for the second group of the magnetic structures.
 2. Therotor-stator structure of claim 1 further comprising: magnetic pathsincluding the confronting surfaces, the field pole members, and thefirst group of the magnetic structures.
 3. The rotor-stator structure ofclaim 2 wherein the second group of the magnetic structures are disposedexternally to the magnetic paths.
 4. The rotor-stator structure of claim2 wherein the second group of the magnetic structures is configured toenhance flux in the magnetic paths.
 5. The rotor-stator structure ofclaim 1 wherein the second group of the magnetic structures furthercomprises: axial boost magnets, wherein the flux conductor shield is anaxial flux conductor shield.
 6. The rotor-stator structure of claim 1wherein the second group of the magnetic structures further comprises:radial boost magnets, wherein the flux conductor shield is a radial fluxconductor shield.
 7. The rotor-stator structure of claim 1 wherein thepole face portions are disposed outside of the boundary of theconically-shaped space and the confronting surfaces are disposed insideof the boundary of the conically-shaped space, wherein the pole faceportions are disposed at a greater radial distance from the axis ofrotation than the confronting surfaces.
 8. The rotor-stator structure ofclaim 7 wherein the one or more rotor assemblies further comprise: aninner rotor assembly.
 9. The rotor-stator structure of claim 7 whereinthe pole face portions further comprise: concave-shaped pole faceportions.
 10. The rotor-stator structure of claim 1 wherein the poleface portions are disposed inside of the boundary of theconically-shaped space and the confronting surfaces are disposed outsideof the boundary of the conically-shaped space, wherein the confrontingsurfaces are disposed at a greater radial distance from the axis ofrotation than the pole face portions.
 11. The rotor-stator structure ofclaim 10 wherein the one or more rotor assemblies further comprise: anouter rotor assembly.
 12. The rotor-stator structure of claim 10 whereinthe pole face portions further comprise: convex-shaped pole faceportions.
 13. The rotor-stator structure of claim 10 further comprises:another group of the magnetic structures; and another flux conductorshield, wherein the group of the magnetic structures includes outerradial boost magnets and the flux conductor shield is an outer radialflux conductor shield, wherein the another group of the magneticstructures includes inner radial boost magnets and the another fluxconductor shield is an inner radial flux conductor shield.
 14. Therotor-stator structure of claim 10 wherein the group of the magneticstructures comprises: breadloaf magnets.
 15. A rotor-stator structurefor an electrodynamic machine comprising: a rotor in which rotorassemblies are arranged on an axis of rotation, each of the rotorassemblies comprising: an arrangement of magnetic regions comprising:magnetically permeable structures positioned radially about the axis ofrotation, the magnetically permeable structures comprising confrontingsurfaces, and non-confronting surfaces, and magnetic materialinterleaved with the magnetically permeable structures; axial boostmagnets; one or more axial flux conductor shields configured to providereturn magnetic paths for the axial boost magnets; radial boost magnets;one or more radial flux conductor shields configured to provide returnmagnetic paths for the radial boost magnets; and field pole membersarranged about the axis and including pole faces at the ends of thefield pole members, a subset of the pole faces being positioned toconfront the arrangement of the magnetic regions to establish air gaps.16. The rotor-stator structure of claim 15 wherein the confrontingsurfaces further comprise: angled confronting surfaces oriented at anangle to the axis and disposed coextensive with a portion of aconically-shaped space centered on the axis of rotation.
 17. Therotor-stator structure of claim 16 wherein the rotor assemblies furthercomprise: outer rotor assemblies.
 18. The rotor-stator structure ofclaim 17 wherein the radial boost magnets further comprise: inner radialboost magnets; and outer radial boost magnets.
 19. The rotor-statorstructure of claim 16 wherein the rotor assemblies further comprise:inner rotor assemblies.
 20. The rotor-stator structure of claim 19wherein the radial boost magnets further comprise: outer radial boostmagnets.
 21. The rotor-stator structure of claim 19 wherein the radialboost magnets further comprise: inner boost magnets.